Professor Bertram Opitz

Professor in Neuroimaging and Cognitive Neuroscience
Chair of the Faculty of Arts and Human Sciences Ethics Committee

Qualifications: Dipl Biophys (Moscow), PhD (Leipzig)

Email:
Phone: Work: 01483 68 9449
Room no: 28 AC 04

Office hours

During academic semesters, I am available to see students in my office (28AC04) on a drop-in basis on Tuesdays & Wednesdays from 2pm until 3pm. Outside these times, scheduled individual appointments can be arranged by emailing me.

Further information

Biography

Bertram Opitz studied Biophysics at the Russian State University in Moscow, Russia. He was a PhD student at the Max-Planck-Institute for Human Cognitive and Brain Sciences, Leipzig and received his doctoral degree in 2000. Until autumn 2001 he continued working as a post-doc researcher and then moved to Saarland University as an Assistant Professor for Cognitive Neuroscience. Bertram joined the Brain & Behaviour Group in August 2012 as a Professor for Neuroimaging.

Research Interests

My research focuses on the neural underpinnings of learning and memory. I'm primarily interested in the neural mechanisms of language acquisition and what factors influence the learning process. Current projects aiming on the role of learning instructions and feedback on (mainly second) language acquisition.

I'm also interested in the functional architecture of different memory systems and the processes by which information is transferred between these memory systems. In current research projects I investigate the processes of creating new enduring memory traces and modulating existing ones. Other projects focus on how we can exert control over our memories, and how these control processes could be trained. The main focus of these projects lies on training induced changes in the neural network in healthy participants and patient samples.

To achieve a comprehensive understanding of learning and memory systems I primarily examine the neural organization of these systems using well established neuroimaging techniques, like event-related potentials and functional magnetic resonance tomography in combination with neural stimulation techniques like transcranial magnetic stimulation (TMS) to investigate the neural correlates of learning and memory.

Publications

Journal articles

  • Shao H, Weng X, Opitz B, Yang J. (2015) 'Recollection reduces unitised familiarity effect'. Memory,

    Abstract

    Two types of encoding tasks have been employed in previous research to investigate the beneficial effect of unitisation on familiarity-based associative recognition (unitised familiarity effect), namely the compound task and the interactive imagery task. Here we show how these two tasks could differentially engage subsequent recollection-based associative recognition and consequently lead to the turn-on or turn-off of the unitised familiarity effect. In the compound task, participants studied unrelated word pairs as newly learned compounds. In the interactive imagery task, participants studied the same word pairs as interactive images. An associative recognition task was used in combination with the Remember/Know procedure to measure recollection-based and familiarity-based associative recognition. The results showed that the unitised familiarity effect was present in the compound task but was absent in the interactive imagery task. A comparison of the compound and the interactive imagery task revealed a dramatic increase in recollection-based associative recognition for the interactive imagery task. These results suggest that unitisation could benefit familiarity-based associative recognition; however, this effect will be eliminated when the memory trace formed is easily accessed by strong recollection without the need for a familiarity assessment.

  • Opitz B, Hofmann J. (2015) 'Concurrence of rule- and similarity-based mechanisms in artificial grammar learning'. Cognitive Psychology, 77, pp. 77-99.

    Abstract

    A current theoretical debate regards whether rule-based or similarity-based learning prevails during artificial grammar learning (AGL). Although the majority of findings are consistent with a similarity-based account of AGL it has been argued that these results were obtained only after limited exposure to study exemplars, and performance on subsequent grammaticality judgment tests has often been barely above chance level. In three experiments the conditions were investigated under which rule- and similarity-based learning could be applied. Participants were exposed to exemplars of an artificial grammar under different (implicit and explicit) learning instructions. The analysis of receiver operating characteristics (ROC) during a final grammaticality judgment test revealed that explicit but not implicit learning led to rule knowledge. It also demonstrated that this knowledge base is built up gradually while similarity knowledge governed the initial state of learning. Together these results indicate that rule- and similarity-based mechanisms concur during AGL. Moreover, it could be speculated that two different rule processes might operate in parallel; bottom-up learning via gradual rule extraction and top-down learning via rule testing. Crucially, the latter is facilitated by performance feedback that encourages explicit hypothesis testing.

  • Bader R, Opitz B, Reith W, Mecklinger A. (2014) 'Is a novel conceptual unit more than the sum of its parts?: FMRI evidence from an associative recognition memory study.'. Neuropsychologia, England: 61, pp. 123-134.

    Abstract

    Recollection, an effortful process relying on the integrity of a brain network including the hippocampus, is generally required to remember arbitrary associations whereas a simple familiarity signal arising in the perirhinal cortex is sufficient to recognize single items. However, the integration of separate items into a single configuration (unitization) leads to reduced involvement of recollection and greater reliance on familiarity. This seems to imply that unitized associations are processed similar to single items. Here, using functional magnetic resonance imaging, we investigated the effects of unitization as encoding strategy on retrieval processes in a between-group-design. A definition was provided that allows combining two unrelated words into a novel conceptual unit (e.g., milk taxi = a delivery service, which is directly dispatched from a farm). We compared this to an encoding strategy in which the words were studied as parts of a sentence. We included pairs in reversed order at test because reversing a unitized word pair is assumed to disrupt the unit while leaving item familiarity for the single constituents intact. This enabled us to compare recognition memory for novel units and single items. Sentence encoding led to a flexible recruitment of brain areas previously associated with recollection, irrespective of the order of the test pair. Unitization encoding reduced the involvement of the recollection network and specifically engaged regions within the parahippocampal cortex and the medial prefrontal cortex for novel units. In contrast, recognition of reversed pairs involved activation of BA 45 in the left inferior frontal gyrus. This possibly suggests that familiarity for novel units and single items are associated with different brain networks.

  • Opitz B. (2014) 'Memory function and the hippocampus'. The Hippocampus in Clinical Neuroscience, 34, pp. 51-59.

    Abstract

    There has been a long tradition in memory research of adopting the view of a vital role of the medial temporal lobe and especially the hippocampus in declarative memory. Despite the broad support for this notion, there is an ongoing debate about what computations are performed by the different substructures. The present chapter summarizes several accounts of hippocampal functions in terms of the cognitive processes subserved by these structures, the information processed, and the underlying neural operations. Firstly, the value of the distinction between recollection and familiarity for the understanding of the role the hippocampus plays in memory is discussed. Then multiple lines of evidence for the role of the hippocampus in memory are considered. Cumulating evidence suggests that the hippocampus fosters the binding of disparate cortical representations of items and their spatiotemporal context into a coherent representation by means of a sparse conjunctive neural coding. This association of item and context will then lead to the phenomenological experience of recollection. In contrast, surrounding cortical areas have broader neural coding that provide a scalar signal of the similarity between two inputs (e.g. between the encoding and the retrieval). By this they form the basis of a feeling of familiarity, but also might encode the commonalities between these different inputs. However, a more complete picture of the importance of the hippocampus for declarative memories can only be drawn when the interactions of the medial temporal lobe with other brain areas are also taken into account.

  • Opitz B. (2014) 'Memory function and the hippocampus.'. Front Neurol Neurosci, Switzerland: 34, pp. 51-59.

    Abstract

    There has been a long tradition in memory research of adopting the view of a vital role of the medial temporal lobe and especially the hippocampus in declarative memory. Despite the broad support for this notion, there is an ongoing debate about what computations are performed by the different substructures. The present chapter summarizes several accounts of hippocampal functions in terms of the cognitive processes subserved by these structures, the information processed, and the underlying neural operations. Firstly, the value of the distinction between recollection and familiarity for the understanding of the role the hippocampus plays in memory is discussed. Then multiple lines of evidence for the role of the hippocampus in memory are considered. Cumulating evidence suggests that the hippocampus fosters the binding of disparate cortical representations of items and their spatiotemporal context into a coherent representation by means of a sparse conjunctive neural coding. This association of item and context will then lead to the phenomenological experience of recollection. In contrast, surrounding cortical areas have broader neural coding that provide a scalar signal of the similarity between two inputs (e.g. between the encoding and the retrieval). By this they form the basis of a feeling of familiarity, but also might encode the commonalities between these different inputs. However, a more complete picture of the importance of the hippocampus for declarative memories can only be drawn when the interactions of the medial temporal lobe with other brain areas are also taken into account.

  • Ferdinand NK, Opitz B. (2014) 'Different aspects of performance feedback engage different brain areas: disentangling valence and expectancy in feedback processing.'. Sci Rep, England: 4

    Abstract

    Evaluating the positive and negative outcomes of our behaviour is important for action selection and learning. Such reinforcement learning has been shown to engage a specific neural circuitry including the mesencephalic dopamine system and its target areas, the striatum and medial frontal cortex, especially the anterior cingulate cortex (ACC). An intensively pursued debate regards the prevailing influence of feedback expectancy and feedback valence on the engagement of these two brain regions in reinforcement learning and their respective roles are far from being understood. To this end, we used a time estimation task with three different types of feedback that allows disentangling the effect of feedback valence and expectancy using functional magnetic resonance imaging (fMRI). Our results show greater ACC activation after unexpected positive and unexpected negative feedback than after expected feedback and by this sensitivity to unexpected events in general irrespective of their valence.

  • Nickels S, Opitz B, Steinhauer K. (2013) 'ERPs show that classroom-instructed late second language learners rely on the same prosodic cues in syntactic parsing as native speakers'. Neuroscience Letters, 557 (PB), pp. 107-111.

    Abstract

    The loss of brain plasticity after a 'critical period' in childhood has often been argued to prevent late language learners from using the same neurocognitive mechanisms as native speakers and, therefore, from attaining a high level of second language (L2) proficiency [7,11]. However, more recent behavioral and electrophysiological research has challenged this 'Critical Period Hypothesis', demonstrating that even late L2 learners can display native-like performance and brain activation patterns [17], especially after longer periods of immersion in an L2 environment. Here we use event-related potentials (ERPs) to show that native-like processing can also be observed in the largely under-researched domain of speech prosody - even when L2 learners are exposed to their second language almost exclusively in a classroom setting. Participants listened to spoken sentences whose prosodic boundaries would either cooperate or conflict with the syntactic structure. Previous work had shown that this paradigm is difficult for elderly native speakers, however, German L2 learners of English showed very similar ERP components for on-line prosodic phrasing as well as for prosody-syntax mismatches (garden path effects) as the control group of native speakers. These data suggest that L2 immersion is not always necessary to master complex L2 speech processing in a native-like way. © 2013 Elsevier Ireland Ltd.

  • Opitz B, Schneiders JA, Mecklinger A, Krick CM. (2013) 'Selective transfer of visual working memory training on Chinese character learning'. Neuropsychologia, 53 (1), pp. 1-11.

    Abstract

    Previous research has shown a systematic relationship between phonological working memory capacity and second language proficiency for alphabetic languages. However, little is known about the impact of working memory processes on second language learning in a non-alphabetic language such as Mandarin Chinese. Due to the greater complexity of the Chinese writing system we expect that visual working memory rather than phonological working memory exerts a unique influence on learning Chinese characters. This issue was explored in the present experiment by comparing visual working memory training with an active (auditory working memory training) control condition and a passive, no training control condition. Training induced modulations in language-related brain networks were additionally examined using functional magnetic resonance imaging in a pretest-training-posttest design. As revealed by pre- to posttest comparisons and analyses of individual differences in working memory training gains, visual working memory training led to positive transfer effects on visual Chinese vocabulary learning compared to both control conditions. In addition, we found sustained activation after visual working memory training in the (predominantly visual) left infero-temporal cortex that was associated with behavioral transfer. In the control conditions, activation either increased (active control condition) or decreased (passive control condition) without reliable behavioral transfer effects. This suggests that visual working memory training leads to more efficient processing and more refined responses in brain regions involved in visual processing. Furthermore, visual working memory training boosted additional activation in the precuneus, presumably reflecting mental image generation of the learned characters. We, therefore, suggest that the conjoint activity of the mid-fusiform gyrus and the precuneus after visual working memory training reflects an interaction of working memory and imagery processes with complex visual stimuli that fosters the coherent synthesis of a percept from a complex visual input in service of enhanced Chinese character learning. © 2013 Elsevier Ltd.

  • Brod G, Opitz B. (2012) 'Does it really matter? Separating the effects of musical training on syntax acquisition.'. Frontiers in Psychology, Switzerland: 3

    Abstract

    The possible transfer of musical expertise to the acquisition of syntactical structures in first and second language has emerged recently as an intriguing topic in the research of cognitive processes. However, it is unlikely that the benefits of musical training extend equally to the acquisition of all syntactical structures. As cognitive transfer presumably requires overlapping processing components and brain regions involved in these processing components, one can surmise that transfer between musical ability and syntax acquisition would be limited to structural elements that are shared between the two. We propose that musical expertise transfers only to the processing of recursive long-distance dependencies inherent in hierarchical syntactic structures. In this study, we taught fifty-six participants with widely varying degrees of musical expertise the artificial language BROCANTO, which allows the direct comparison of long-distance and local dependencies. We found that the quantity of musical training (measured in accumulated hours of practice and instruction) explained unique variance in performance in the long-distance dependency condition only. These data suggest that musical training facilitates the acquisition specifically of hierarchical syntactic structures.

  • Opitz B, Degner J. (2012) 'Emotionality in a second language: it's a matter of time.'. Neuropsychologia, England: 50 (8), pp. 1961-1967.

    Abstract

    The present study investigated the well acknowledged phenomenon of a different sense of emotionality in a person's first (L1) and second language (L2). Event-related potentials were recorded during the reading of pleasant, unpleasant and neutral words in L1 and L2. Enhanced processing of both emotional compared to neutral words was reflected in an amplified early posterior negativity (EPN) about 280–430 ms after word onset. While the EPN did not differ in amplitude between L1 and L2, it was delayed for L2. Interestingly, a better task performance in L2 but not L1 predicted longer delays of the EPN. These results might indicate that the affective valence of L2 words is processed in a less immediate way due to delayed lexical access. This is interpreted in terms of interference in a highly integrated L1/L2 mental lexicon.

  • Opitz B, Kotz SA. (2012) 'Ventral premotor cortex lesions disrupt learning of sequential grammatical structures.'. Cortex, Italy: 48 (6), pp. 664-673.

    Abstract

    Recent functional magnetic resonance imaging (fMRI) evidence shows differential involvement of the inferior frontal gyrus (IFG) and the ventral premotor cortex (PMv) in syntactic processing. Our main goal is to specify the precise role of the PMv in the processing of sequential structures and whether these processes are a necessary prerequisite for the successful acquisition of grammatical structure.

  • Hauser MF, Hofmann J, Opitz B. (2012) 'Rule and similarity in grammar: their interplay and individual differences in the brain.'. Neuroimage, United States: 60 (4), pp. 2019-2026.

    Abstract

    Previous research on artificial grammar has indicated that the human ability to classify sentences or letter strings according to grammaticality relies on two types of knowledge. One is a superficial, familiarity-based understanding of a grammar the other is the knowledge of rules and critical features underlying a grammar. The fundamentally different characteristics of these systems permit an analysis of receiver-operating characteristics (ROC), which measures the extent to which each type of knowledge is used in grammaticality judgments. Furthermore, violations of a grammar can be divided into hierarchical and local violations. The present study is the first to combine the use of ROC analyses, fMRI and a grammaticality dichotomy. Based on previous neuroimaging studies, it was hypothesized that judgments based on rule knowledge, as extracted from individual ROC analyses, involve the left inferior frontal gyrus (IFG), whereas similarity would involve right IFG, as well as left hippocampal regions. With regards to violation types, it was hypothesized that hierarchical violations would recruit the opercular part of the left IFG as well as the posterior operculum, whereas local violations would bilaterally activate the premotor cortex (PMC). Results indicated that for greater reliance on rule knowledge, a ventral part of the left PMC was activated for ungrammatical items, whereas other PMC areas show a differentiated response for grammaticality for individuals less reliant on similarity. The right IFG was related to ungrammatical items as a function of similarity. Results are discussed with regards to possible error detection systems and differentiated efficiencies for respective classification strategies.

  • Kipp KH, Opitz B, Becker M, Hofmann J, Krick C, Gortner L, Mecklinger A. (2012) 'Neural correlates of recognition memory in children with febrile seizures: evidence from functional magnetic resonance imaging.'. Frontiers in Human Neuroscience, Switzerland: 6

    Abstract

    Febrile seizures (FS) are assumed to not have adverse long-term effects on cognitive development. Nevertheless, FS are often associated with hippocampal sclerosis which can imply episodic memory deficits. This interrelation has hardly been studied so far. In the current study 13 children who had suffered from FS during infancy and 14 control children (7 to 9-years-old) were examined for episodic and semantic memory with standardized neuropsychological tests. Furthermore, using functional magnetic resonance imaging (fMRI) we studied neuronal activation while the children performed a continuous recognition memory task. The analysis of the behavioral data of the neuropsychological tests and the recognition memory experiment did not reveal any between-group differences in memory performance. Consistent with other studies fMRI revealed repetition enhancement effects for both groups in a variety of brain regions (e.g., right middle frontal gyrus, left parahippocampal gyrus) and a repetition suppression effect in the right superior temporal gyrus. Different neural activation patterns between both groups were obtained selectively within the right supramarginal gyrus (BA 40). In the control group correct rejections of new items were associated with stronger activation than correctly identified old items (HITs) whereas in the FS group no difference occurred. On the background that the right supramarginal gyrus is assumed to mediate a top-down process to internally direct attention toward recollected information, the results could indicate that control children used strategic recollection in order to reject new items (recall-to-reject). In contrast, the missing effect in the FS group could reflect a lack of strategy use, possibly due to impaired recollective processing. This study demonstrates that FS, even with mainly benign courses, can be accompanied by selective modifications in the neural structures underlying recognition memory.

  • Kipp KH, Opitz B, Becker M, Hofmann J, Mecklinger A, Krick C, Gortner L. (2012) 'Selective modifications in the neural memory network in children with febrile seizures: Evidence from functional magnetic resonance imaging'. Frontiers in Human Neuroscience, (JANUARY 2012)

    Abstract

    Febrile seizures (FS) are assumed to not have adverse long-term effects on cognitive development. Nevertheless, FS are often associated with hippocampal sclerosis which can imply episodic memory deficits. This interrelation has hardly been studied so far. In the current study 13 children who had suffered from FS during infancy and 14 control children (7-9 years old) were examined for episodic and semantic memory with standardized neuropsychological tests. Furthermore, using functional magnetic resonance imaging (fMRI) we studied neuronal activation while the children performed a continuous recognition memory task. The analysis of the behavioral data of the neuropsychological tests and the recognition memory experiment did not reveal any between group differences in memory performance. Consistent with other studies fMRI revealed repetition enhancement effects for both groups in a variety of brain regions (e.g. right middle frontal gyrus, left parahippocampal gyrus) and a repetition suppression effect in the right superior temporal gyrus. Different neural activation patterns between both groups were obtained selectively within the right supramarginal gyrus (BA 40). In the control group correct rejections of new items (CRs) were associated with stronger activation than correctly identified old items (HITs) whereas in the FS group no difference occurred. On the background that the right supramarginal gyrus is assumed to mediate a top-down process to internally direct attention towards recollected information, the results could indicate that control children used strategic recollection in order to reject new items (recall-to-reject). In contrast, the missing effect in the FS group could reflect a lack of strategy use, possibly due to impaired recollective processing. This study demonstrates that FS, even with mainly benign courses, can be accompanied by selective modifications in the neural structures underlying recognition memory. © 2012 Kipp, Opitz, Becker, Hofmann, Krick, Gortner and Mecklinger.

  • Kipp KH, Opitz B, Becker M, Hofmann J, Mecklinger A, Krick C, Gortner L. (2012) 'Selective modifications in the neural memory network in children with febrile seizures: Evidence from functional magnetic resonance imaging'. Frontiers in Human Neuroscience, (JANUARY 2012)

    Abstract

    Febrile seizures (FS) are assumed to not have adverse long-term effects on cognitive development. Nevertheless, FS are often associated with hippocampal sclerosis which can imply episodic memory deficits. This interrelation has hardly been studied so far. In the current study 13 children who had suffered from FS during infancy and 14 control children (7-9 years old) were examined for episodic and semantic memory with standardized neuropsychological tests. Furthermore, using functional magnetic resonance imaging (fMRI) we studied neuronal activation while the children performed a continuous recognition memory task. The analysis of the behavioral data of the neuropsychological tests and the recognition memory experiment did not reveal any between group differences in memory performance. Consistent with other studies fMRI revealed repetition enhancement effects for both groups in a variety of brain regions (e.g. right middle frontal gyrus, left parahippocampal gyrus) and a repetition suppression effect in the right superior temporal gyrus. Different neural activation patterns between both groups were obtained selectively within the right supramarginal gyrus (BA 40). In the control group correct rejections of new items (CRs) were associated with stronger activation than correctly identified old items (HITs) whereas in the FS group no difference occurred. On the background that the right supramarginal gyrus is assumed to mediate a top-down process to internally direct attention towards recollected information, the results could indicate that control children used strategic recollection in order to reject new items (recall-to-reject). In contrast, the missing effect in the FS group could reflect a lack of strategy use, possibly due to impaired recollective processing. This study demonstrates that FS, even with mainly benign courses, can be accompanied by selective modifications in the neural structures underlying recognition memory. © 2012 Kipp, Opitz, Becker, Hofmann, Krick, Gortner and Mecklinger.

  • Schneiders JA, Opitz B, Tang H, Deng Y, Xie C, Li H, Mecklinger A. (2012) 'The impact of auditory working memory training on the fronto-parietal working memory network.'. Frontiers in Human Neuroscience, Switzerland: 6

    Abstract

    Working memory training has been widely used to investigate working memory processes. We have shown previously that visual working memory benefits only from intra-modal visual but not from across-modal auditory working memory training. In the present functional magnetic resonance imaging study we examined whether auditory working memory processes can also be trained specifically and which training-induced activation changes accompany theses effects. It was investigated whether working memory training with strongly distinct auditory materials transfers exclusively to an auditory (intra-modal) working memory task or whether it generalizes to a (across-modal) visual working memory task. We used adaptive n-back training with tonal sequences and a passive control condition. The memory training led to a reliable training gain. Transfer effects were found for the (intra-modal) auditory but not for the (across-modal) visual transfer task. Training-induced activation decreases in the auditory transfer task were found in two regions in the right inferior frontal gyrus. These effects confirm our previous findings in the visual modality and extents intra-modal effects in the prefrontal cortex to the auditory modality. As the right inferior frontal gyrus is frequently found in maintaining modality-specific auditory information, these results might reflect increased neural efficiency in auditory working memory processes. Furthermore, task-unspecific (amodal) activation decreases in the visual and auditory transfer task were found in the right inferior parietal lobule and the superior portion of the right middle frontal gyrus reflecting less demand on general attentional control processes. These data are in good agreement with amodal activation decreases within the same brain regions on a visual transfer task reported previously.

  • Schneiders JA, Opitz B, Krick CM, Mecklinger A. (2011) 'Separating intra-modal and across-modal training effects in visual working memory: an fMRI investigation.'. Cerebral Cortex, United States: 21 (11), pp. 2555-2564.

    Abstract

    Working memory training is a useful tool to examine dissociations between specific working memory processes. Although current models propose a distinction between modality-specific working memory processes, to our knowledge no study has directly examined the effects of visual versus auditory working memory training. Functional magnetic resonance imaging was used to investigate whether visual working memory processes can be trained specifically and whether those effects can be separated from across-modal training effects. We found decidedly larger training gains after visual working memory training compared with auditory or no training on a visual 2-back task. These effects were accompanied by specific training-related decreases in the right middle frontal gyrus arising from visual training only. Likewise, visual and auditory training led to decreased activations in the superior portion of the right middle frontal gyrus and the right posterior parietal lobule. We infer that the combination of effects resulted from increased neural efficiency of intra-modal (visual) processes on the one hand and of across-modal (general control) processes on the other hand. Therefore, visual processes of working memory can be trained specifically, and these effects can be functionally dissociated from alterations in general control processes common to both working memory trainings.

  • Opitz B, Ferdinand NK, Mecklinger A. (2011) 'Timing matters: the impact of immediate and delayed feedback on artificial language learning.'. Frontiers in Human Neuroscience, Switzerland: 5

    Abstract

    In the present experiment, we used event-related potentials (ERP) to investigate the role of immediate and delayed feedback in an artificial grammar learning (AGL) task. Two groups of participants were engaged in classifying non-word strings according to an underlying rule system, not known to the participants. Visual feedback was provided after each classification either immediately or with a short delay of 1 s. Both groups were able to learn the artificial grammar system as indicated by an increase in classification performance. However, the gain in performance was significantly larger for the group receiving immediate feedback as compared to the group receiving delayed feedback. Learning was accompanied by an increase in P300 activity in the ERP for delayed as compared to immediate feedback. Irrespective of feedback delay, both groups exhibited learning related decreases in the feedback-related positivity (FRP) elicited by positive feedback only. The feedback-related negativity (FRN), however, remained constant over the course of learning. These results suggest, first, that delayed feedback is less effective for AGL as task requirements are very demanding, and second, that the FRP elicited by positive prediction errors decreases with learning while the FRN to negative prediction errors is elicited in an all-or-none fashion by negative feedback throughout the entire experiment.

  • Opitz B. (2010) 'Neural binding mechanisms in learning and memory.'. Neuroscience and Biobehavioral Reviews, United States: 34 (7), pp. 1036-1046.

    Abstract

    Binding mechanisms are considered as basic cognitive operations, performing different functions in learning and memory. This review will cover two of these binding mechanisms: relational binding of information about stimuli and actions with their spatio-temporal context into a circumscribed cognitive event and representational binding of feature representations common to a number of such events, thereby integrating these representations with existing knowledge and, thus, leading to decontextualized knowledge about the world. I will survey evidence from recent neuropsychological, electrophysiological and neuroimaging studies, including my own work, demonstrating that relational binding operations are performed within the hippocampal system, whereas representational binding is subserved by the surrounding medial-temporal lobe cortex and prefrontal brain areas. I then present examples of conditions that differentially implement both binding mechanisms. Lastly, summarizing the extant literature on binding mechanisms I speculate on whether these binding mechanism operate in a similar way across different cognitive domains or whether they are domain-specific.

  • Opitz B. (2010) 'Context-dependent repetition effects on recognition memory.'. Brain and Cognition, United States: 73 (2), pp. 110-118.

    Abstract

    One widely acknowledged way to improve our memory performance is to repeatedly study the to be learned material. One aspect that has received little attention in past research regards the context sensitivity of this repetition effect, that is whether the item is repeated within the same or within different contexts. The predictions of a neuro-computational model (O'Reilly & Norman, 2002) were tested in an experiment requiring participants to study visual objects either once or three times. Crucially, for half of the repeated objects the study context (encoding task, background color and screen position) remained the same (within context repetition) while for the other half the contextual features changed across repetitions (across context repetition). In addition to behavioral measures, event-related potentials (ERP) were recorded that provide complementary information on the underlying neural mechanisms during recognition. Consistent with dual-process models behavioral estimates (remember/know-procedure) demonstrate differential effects of context on memory performance, namely that recognition judgements were more dependent on familiarity when repetition occurs across contexts. In accordance with these behavioral results ERPs showed a larger early frontal old/new effect for across context repetitions as compared to within context repetitions and single presentations, i.e. an increase in familiarity following repetition across study contexts. In contrast, the late parietal old/new effect, indexing recollection did not differ between both repetition conditions. These results suggest that repetition differentially affects familiarity depending on whether it occurs within the same context or across different contexts.

  • Spitzer B, Hanslmayr S, Opitz B, Mecklinger A, Baeuml K-H. (2009) 'Oscillatory Correlates of Retrieval-induced Forgetting in Recognition Memory'. Journal of Cognitive Neuroscience, 21 (5), pp. 976-990.

    Abstract

    Retrieval practice on a subset of previously studied material enhances later memory for practiced material but can inhibit memory for related unpracticed material. The present study examines the effects of prior retrieval practice on evoked (ERPs) and induced (oscillatory power) measures of electrophysiological activity underlying recognition of practiced and unpracticed words. Compared to control material, recognition of unpracticed words was characterized by reduced amplitudes of the P2 ERP component and by reduced early (200–400 msec) oscillatory theta power. The reduction in P2 amplitude was associated with decreased evoked theta power but not with decreased theta phase locking (phase-locking index). Recognition of unpracticed material was further accompanied by a reduction in occipital gamma power (>250 msec). In contrast, the beneficial effects of retrieval practice on practiced words were reflected by larger parietal ERP positivity (>500 msec) and by a stronger decrease in oscillatory alpha power in a relatively late time window (>700 msec). The results suggest that the beneficial and detrimental effects of retrieval practice are mediated by different processes. In particular, they suggest that reduced theta (4–7 Hz) and gamma (60–90 Hz) power reflect the specific effects of inhibitory processes on the unpracticed material's memory representation.

  • Opitz B, Friederici AD. (2007) 'Neural basis of processing sequential and hierarchical syntactic structures.'. Hum Brain Mapp, United States: 28 (7), pp. 585-592.

    Abstract

    The psychological processes through which humans learn a language have gained considerable interest over the past years. It has been previously suggested that language acquisition partly relies on a rule-based mechanism that is mediated by the frontal cortex. Interestingly, the actual structure involved within the frontal cortex varies with the kind of rules being processed. By means of functional MRI we investigated the neural underpinnings of rule-based language processing using an artificial language that allows direct comparisons between local phrase structure dependencies and hierarchically structured long-distance dependencies. Activation in the left ventral premotor cortex (PMC) was related to the local character of rule change, whereas long-distance dependencies activated the opercular part of the inferior frontal gyrus (Broca's area (BA) 44). These results suggest that the brain's involvement in syntactic processing is determined by the type of rule used, with BA 44/45 playing an important role during language processing when long-distance dependencies are processed. In contrast, the ventral PMC seems to subserve the processing of local dependencies. In addition, hippocampal activity was observed for local dependencies, indicating that the processing of such dependencies may be mediated by a second mechanism.

  • Kotz SA, Opitz B, Friederici AD. (2007) 'ERP effects of meaningful and non-meaningful sound processing in anterior temporal patients'. RESTORATIVE NEUROLOGY AND NEUROSCIENCE, 25 (3-4), pp. 273-284.
  • Opitz B, Cornell S. (2006) 'Contribution of familiarity and recollection to associative recognition memory: insights from event-related potentials.'. J Cogn Neurosci, United States: 18 (9), pp. 1595-1605.

    Abstract

    Within the dual-process perspective of recognition memory, it has been claimed that familiarity is sufficient to support recognition of single items, but recollection is necessary for associative recognition of item pairs. However, there are some reports suggesting that familiarity might support associative recognition judgments when the items form an easy to access bound representation. In contrast, recollection seems to be required for the recognition of bindings that might be flexibly rearranged in novel situations. We investigated whether both forms of binding are mediated by different mechanisms as reflected by a qualitatively different spatiotemporal eventrelated potential (ERP) pattern. In a recognition memory experiment, subjects gave old/new judgments to words learned by focusing either on interitem associations or on size relation of word triplets. Results revealed higher hit rates in the relational condition as compared to the associative condition. In addition, the proportion of triplets from which all three items were remembered was significantly larger in the relational condition suggesting that memory retrieval in this condition relies primarily on bound representations of word triplets. The ERP revealed a late parietal old/new effect for both conditions, with relational processing resulting in a greater effect. In contrast, an early frontal old/new effect was solely present in the associative condition. Taken together, these data provide evidence that familiarity might support associative recognition if the associated components are coherently encoded into a bound representation. Recollection might foster the recognition of relational bindings among items. This indicates that the contribution of familiarity and recollection to associative recognition depends on the kind of binding operations performed on the items rather than on the single versus multiple item distinction.

  • Doeller CF, Opitz B, Krick CM, Mecklinger A, Reith W. (2006) 'Differential hippocampal and prefrontal-striatal contributions to instance-based and rule-based learning'. NEUROIMAGE, 31 (4), pp. 1802-1816.

Posters

  • Schneiders JA, Opitz B, Weng X, Mecklinger A. (2010) Auditory Working Memory Training Leads to Specific Decreases in Left Prefrontal Cortex When Learning The Phonology Of Chinese Words. Fiftieth Annual Meeting of the Society for Psychophysiological Research

    Abstract

    Logographic Chinese differs from alphabetic languages in aspects of orthography and phonology. While there are different neural networks involved in processing orthography across these language systems, there is evidence for a common neural network across languages for auditory phonology. Since lexical tones are phonemically relevant in Chinese only, learning Chinese phonology should benefit more from auditory than visual working memory (WM) training and result in activation decreases in its underlying neural circuitry. We used an n-back WM training procedure to investigate the differential impact of auditory and visual WM training on phonological proficiency while Germans learned the phonology of Chinese words. Training-inducedmodulations in language-related networkswere examined bymeans offMRI. Behavioral data did not show any transfer from auditory and visual WM training to phonological proficiency compared to a control group. Brain imaging analyses during pretest revealed activations in the left medial frontal gyrus, anterior cingulate gyrus and pallidum. Importantly, volume-of-interest analyses in these regions showed training-induced activation decreases in the medial frontal gyrus for the auditory training group but not for the other two groups. These results suggest that the training of auditoryWMleads - even in the absence of behavioral transfer effects - to more efficient processing within the left dorsal prefrontal cortex when learning Chinese phonology probably reflecting facilitated attentional selection of phonetic information in spoken Chinese words.

  • Opitz B. (2009) Can repetition lead to semantic knowledge?. 49th Annual Meeting of the Society-for-Psychophysiological-Research

    Abstract

    Memory enhancement after repeated presentation of to-be-learned material is a wellknown phenomenon. It has been assumed that the repeated presentation of features common to a number of specific instances leads to decontextualized facts about the world, i.e., semantic knowledge. To investigate this issue, subjects studied celebrity faces along with faces of unknown individuals. Crucially, half of the unknown faces were repeated within the same study context (background and biographical information) while for the other half the contextual features changed across repetitions. Celebrity faces were chosen because they carry with them biographical information. The electrophysiological correlates of conceptual priming and explicit memory for these faces were examined. Explicit memory retrieval was associated with the early frontal old/new effect, the ERP correlate of familiarity, and the late parietal old/new effect, indexing recollection. Both ERP effects were elicited by celebrity faces and non-famous faces repeatedly studied in different contexts, whereas non-famous faces repeated in the same context elicited only the parietal old/new effect. Furthermore, conceptual priming was indexed by positive brain potentials over fronto-central regions, in addition to faster reaction times for previously presented faces. Again, a striking similarity between effects elicited by celebrity faces and non-famous faces repeated in varying contexts was observed. This indicates that repetition of features across different contexts bears some similarity to semantic knowledge.

Departmental Duties

Chair of the Faculty of Arts and Human Sciences Ethics Committee

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