Zeynel Baran

A comprehensive neuropsychological mapping battery for functional magnetic resonance imaging.

Existing batteries for FMRI do not precisely meet the criteria for comprehensive mapping of cognitive functions within minimum data acquisition times using standard scanners and head coils. The goal was to develop a battery of neuropsychological paradigms for FMRI that can also be used in other brain imaging techniques and behavioural research. Participants were 61 healthy, young adult volunteers (48 females and 13 males, mean age: 22.25 ± 3.39 years) from the university community. The battery included 8 paradigms for basic (visual, auditory, sensory-motor, emotional arousal) and complex (language, working memory, inhibition/interference control, learning) cognitive functions. Imaging was performed using standard functional imaging capabilities (1.5-T MR scanner, standard head coil). Structural and functional data series were analysed using Brain Voyager QX2.9 and Statistical Parametric Mapping-8. For basic processes, activation centres for individuals were within a distance of 3-11 mm of the group centres of the target regions and for complex cognitive processes, between 7 mm and 15 mm. Based on fixed-effect and random-effects analyses, the distance between the activation centres was 0-4 mm. There was spatial variability between individual cases; however, as shown by the distances between the centres found with fixed-effect and random-effects analyses, the coordinates for individual cases can be used to represent those of the group. The findings show that the neuropsychological brain mapping battery described here can be used in basic science studies that investigate the relationship of the brain to the mind and also as functional localiser in clinical studies for diagnosis, follow-up and pre-surgical mapping.

The Impact of Aging and Alzheimer's Disease on Emotional Enhancement of Memory

Emotional enhancement of memory (EEM) has been a well-known phenomenon which corresponds to the advantage of emotional stimuli to be better recalled than neutral ones. Previous studies suggest that aging favours recollection of positive items and this pattern is disrupted in Alzheimers disease (AD). Emotional valence of different stimulus modalities, i.e. pictures and words, may also have an effect on each others memory performances. However, none of these were clearly studied in AD. This study aimed to evaluate how emotional valences of simultaneously presented stimuli affected recall in healthy young (YG, n = 30), healthy elderly (HE, n = 30) participants and in patients with AD (n = 30). A battery consisting of emotional words presented on emotional pictures was developed. An analysis of a 3 (Groups) × 3 (Emotional Valence of Picture) × 3 (Emotional Valence of Word) mixed ANOVA design was carried out. Patients with AD could process emotional information similarly to healthy participants; however, they had EEM only for picture recalling. Emotional valence of the co-presented stimulus had a boosting effect both in the YG and HE, but not in AD group, especially if both of the stimuli had the same emotional valence. This study highlights the impaired EEM for verbal and preserved EEM for non-verbal declarative memory in patients with AD, the neurobiological underpinnings of which should be addressed by future studies.

Prefrontal activity measured by functional near infrared spectroscopy during probabilistic inference in subjects with persecutory delusions.

Jumping to conclusions (JTC) is a probabilistic reasoning bias and is thought to contribute to delusion formation. Neurobiological correlates of the JTC bias are not known. We aimed to examine the rostral prefrontal cortex (rPFC) activity with functional near ınfrared spectroscopy during a modified version of the Beads in a Jar Task (BIJT) in subjects with persecutory delusions (N=25). In BIJT participants are presented beads either drawn from one of the two jars with opposite probability ratios (PRs) of colored beads and are required to decide from which jar beads are being drawn. We administered the BIJT with 90/10 and 55/45 PRs. Compared to healthy controls (N=20), patients reached a decision earlier in both conditions. While the medial rPFC regions were more active in the 90/10 condition in controls compared to patients, lateral rPFC activation was higher in the 55/45 condition in patients than controls. Only in the control group, there was a marked decline in the lateral rPFC activation in the 55/45 condition compared to the 90/10 condition. The activity in the lateral rPFC was negatively correlated with the amount of beads drawn in healthy controls but not in subjects with persecutory delusions. Our results suggest that during the BIJT, rPFC does not function as a single unit and rather consists of functional subunits that are organized differently in patients and controls. The failure to deactivate the lateral rPFC may be associated with earlier decisions in subjects with persecutory delusions.

Effect of a socıal defeat experıence on prefrontal actıvıty ın schızophrenıa

The social defeat (SD) hypothesis of schizophrenia posits that repeated experiences of SD may lead to sensitization of the mesolimbic dopaminergic system and to precipitation of psychosis. Based on previous definitions adapted to a human experimental paradigm, we prepared a computer simulation of SD to mimic this subjective experience. We measured prefrontal cortex (PFC) activity in subjects with schizophrenia and healthy controls during exposure to a single SD experience with functional near infrared spectroscopy. PFC activity declined in both groups. Compared with the control condition, SD exposure was associated with a broader decline in left ventromedial, right medial and right lateral PFC activity in healthy controls (n=25), and a sharper decline in right ventrolateral PFC activity in subjects with schizophrenia (n=25). The activity in the right ventrolateral PFC, was significantly lower in patients compared with controls. This may be due to a deficiency in emotion regulation or self-control, or it may be related to impaired empathy in schizophrenia. Different patterns of brain activity during the SD experience in subjects with schizophrenia versus healthy controls may provide indirect evidence regarding the SD hypothesis of schizophrenia.

Frontal activity during a verbal emotional working memory task in patients with Alzheimer's disease: A functional near-infrared spectroscopy study

Emotional working memory (EWM) is suggested as a working memory (WM) type, distinguished to process emotional stimuli, and may or may not be spared in Alzheimers disease (AD). The aim was to compare patients with AD and healthy older adults (HC) on verbal EWM performance and accompanying prefrontal cortex activity. Twenty AD patients along with 20 HC individuals are required to complete an emotional one-back task in three conditions (neutral, positive and negative word lists). Prefrontal oxyhemoglobin (oxyHb) concentrations were measured simultaneously by a 24- channel functional near infrared spectroscopy device. Correct response rates were similar in two groups in all conditions. Reaction times were comparable in the EWM positive condition but longer in the AD group in EWMneutral and negative conditions. In the HC group, emotional words had no significant effect on WM. On the other hand, positive compared to neutral words led to greater activation in the left ventral prefrontal cortex (VPFC) in AD group. When compared to HCs, activity in the VPFC was significantly higher in AD patients during the positive condition. Positive words facilitated WM performance in participants with AD. Activity in VPFC may be the functional correlate of this phenomenon.