Dr Erkan Alkan

PhD Student

Academic and research departments

School of Psychology.


Erkan Alkan, Geoff Davies, Kathryn Greenwood, Simon L. H. Evans (2019)Brain Structural Correlates of Metacognition in First-Episode Psychosis, In: Schizophrenia Bulletin Oxford University Press

Metacognition is impaired in schizophrenia and is an important predictor of functional outcome, but the underlying neuropathology is not clear. Studies have implicated frontal regions and there is also some evidence that the hippocampus might play a pivotal role, but findings are inconsistent. We set out to more comprehensively investigate the neural underpinnings of insight in first-episode psychosis (FEP) using 2 metacognitive measures (the Beck Cognitive Insight Scale [BCIS]) and a perceptual metacognitive accuracy task alongside structural magnetic resonance imaging (MRI). We measured cortical thickness in insula and frontal regions, hippocampal (including subfield) volumes, hippocampal microstructure (using neurite orientation dispersion and density imaging [NODDI]), and fractional anisotropy in fornix. Relative to controls, FEP showed poorer metacognitive accuracy, thinner cortex in frontal regions and lower fornix integrity. In healthy controls (but not FEP), metacognitive accuracy correlated with cortical thickness in frontal cortex and insula. Conversely, in FEP (but not controls), metacognitive accuracy correlated with hippocampal volume and microstructural indices. Subicular hippocampal subregions were particularly implicated. No structural correlates of BCIS were found. These findings suggest that the neural bases of metacognition might differ in FEP: hippocampal (rather than frontal) integrity seems to be critical. Further, the use of objectively measured metacognitive indices seems to be a more powerful method for understanding the neurocircuitry of metacognition in FEP, which has the potential to inform therapeutic strategies and improve outcome in these patients.

Erkan Alkan, T P Taporoski, A Sterr, M von Schantz, H Vallada, J E Krieger, A C Pereira, R Alvim, A R V R Horimoto, S Pompéia, A B Negrão, Simon Evans (2019)Metabolic syndrome alters relationships between cardiometabolic variables, cognition and white matter hyperintensity load, In: Scientific Reports94356 Nature Publishing Group

Cardiometabolic risk factors influence white matter hyperintensity (WMH) development: in metabolic syndrome (MetS), higher WMH load is often reported but the relationships between specific cardiometabolic variables, WMH load and cognitive performance are uncertain. We investigated these in a Brazilian sample (aged 50-85) with (N=61) and without (N=103) MetS. Stepwise regression models identified effects of cardiometabolic and demographic variables on WMH load (from FLAIR MRI) and verbal recall performance. WMH volume was greater in MetS, but verbal recall performance was not impaired. Age showed the strongest relationship with WMH load. Across all participants, systolic blood pressure (SBP) and fasting blood glucose were also contributors, and WMH volume was negatively associated with verbal recall performance. In non-MetS, higher HbA1c, SBP, and number of MetS components were linked to poorer recall performance while higher triglyceride levels appeared to be protective. In MetS only, these relationships were absent but education exerted a strongly protective effect on recall performance. Thus, results support MetS as a construct: the clustering of cardiometabolic variables in MetS alters their individual relationships with cognition; instead, MetS is characterised by a greater reliance on cognitive reserve mechanisms. In non-MetS, strategies to control HbA1c and SBP should be prioritised as these have the largest impact on cognition.

Simon Evans, Erkan Alkan, Jazmin K Bhangoo, Harriet Tenenbaum, Terry Ng-Knight (2021)Effects of the COVID-19 lockdown on mental health, wellbeing, sleep, and alcohol use in a UK student sample, In: Psychiatry research298 113819

The COVID-19 pandemic and the consequent restrictions imposed by governments worldwide have had profound social and psychological effects, particularly for young adults. This study used longitudinal data to characterise effects on mental health and behaviour in a UK student sample, measuring sleep quality and diurnal preference, depression and anxiety symptoms, wellbeing and loneliness, and alcohol use. Self-report data was collected from 254 undergraduates (219 females) at a UK university at two-time points: autumn 2019 (baseline, pre-pandemic) and April/May 2020 (under 'lockdown' conditions).  Longitudinal analyses showed a significant rise in depression symptoms and a reduction in wellbeing at lockdown. Over a third of the sample could be classed as clinically depressed at lockdown compared to 15% at baseline. Sleep quality was not affected across the sample as a whole. The increase in depression symptoms was highly correlated with worsened sleep quality. A reduction in alcohol use, and a significant shift towards an 'evening' diurnal preference, were also observed. Levels of worry surrounding contracting COVID-19 were high. Results highlight the urgent need for strategies to support young people's mental health: alleviating worries around contracting COVID, and supporting good sleep quality, could benefit young adults' mental health as the COVID-19 crisis unfolds.

Erkan Alkan, Geoff Davies, Kathy Greenwood, SIMON EVANS (2020)Brain structural correlates of functional capacity in first-episode psychosis, In: Scientific reports10(1)17229 Nature Publishing Group UK

Impaired functional capacity is a core feature of schizophrenia and presents even in first-episode psychosis (FEP) patients. Impairments in daily functioning tend to persist despite antipsychotic therapy but their neural basis is less clear. Previous studies suggest that volume loss in frontal cortex might be an important contributor, but findings are inconsistent. We aimed to comprehensively investigate the brain structural correlates of functional capacity in FEP using MRI and a reliable objective measure of functioning [University of California, San Diego Performance-Based Skills Assessment (UPSA)]. In a sample of FEP (n = 39) and a well-matched control group (n = 21), we measured cortical thickness, gray matter volume, and white matter tract integrity (fractional anisotropy, FA) within brain regions implicated by previous work. The FEP group had thinner cortex in various frontal regions and fusiform, and reduced FA in inferior longitudinal fasciculus (ILF). In FEP, poorer functional capacity correlated with reduced superior frontal volume and lower FA in left ILF. Importantly, frontal brain volumes and integrity of the ILF were identified as the structural correlates of functional capacity in FEP, controlling for other relevant factors. These findings enhance mechanistic understanding of functional capacity deficits in schizophrenia by specifying the underlying neural correlates. In future, this could help inform intervention strategies.

SIMON EVANS, MA Leocadio-Miguel, Tamara P. Taporoski, Luz Marina Gomez, Andréa Horimoto, ERKAN ALKAN, Felipe Beijamini, Mario Pedrazzoli, Kristen L. Knutson, Jose Eduardo Krieger, Homero Vallada, ANNETTE MARIE STERR, Alexandre Pereira, André Negrão, MALCOLM VON SCHANTZ (2021)Evening preference correlates with regional brain volumes in the anterior occipital lobe, In: Chronobiology International Taylor and Francis

Chronotype or diurnal preference is a questionnaire-based measure influenced both by circadian period and by the sleep homeostat. In order to further characterize the biological determinants of these measures, we used a hypothesis-free approach to investigate the association between the score of the morningness-eveningness questionnaire (MEQ) and the Munich chronotype questionnaire (MCTQ), as continuous variables, and volumetric measures of brain regions acquired by magnetic resonance imaging (MRI). Data were collected from the Baependi Heart Study cohort, based in a rural town in South-Eastern Brazil. MEQ and anatomical 1.5-T MRI scan data were available from 410 individuals, and MCTQ scores were available from a subset of 198 of them. The average MEQ (62.2±10.6) and MCTQ (average MSFsc 201±85 min) scores were suggestive of a previously reported strong general tendency towards morningness in this community. Setting the significance threshold at P>0.002 to account for multiple comparisons, we observed a significant association between lower MEQ score (eveningness) and greater volume of the left anterior occipital sulcus (β=-0.163, p=0.001) of the occipital lobe. No significant associations were observed for MCTQ. This may reflect the smaller dataset for MCTQ, and/or the fact that MEQ, which asks questions about preferred timings, is more trait-like than the MCTQ, which asks questions about actual timings. The association between MEQ and a brain region dedicated to visual information processing is suggestive of the increasingly recognized fluidity in the interaction between visual and non-visual photoreception and the circadian system, and the possibility that chronotype includes an element of masking.