Ali Bilgin Arslan

The Language of Actions: Recovering the Syntax and Semantics of Goal-Directed Human Activities

This paper describes a framework for modeling human activities as temporally structured processes. Our approach is motivated by the inherently hierarchical nature of human activities and the close correspondence between human actions and speech: We model action units using Hidden Markov Models, much like words in speech. These action units then form the building blocks to model complex human activities as sentences using an action grammar. To evaluate our approach, we collected a large dataset of daily cooking activities: The dataset includes a total of 52 participants, each performing a total of 10 cooking activities in multiple real-life kitchens, resulting in over 77 hours of video footage. We evaluate the HTK toolkit, a state-of-the-art speech recognition engine, in combination with multiple video feature descriptors, for both the recognition of cooking activities (e.g., making pancakes) as well as the semantic parsing of videos into action units (e.g., cracking eggs). Our results demonstrate the benefits of structured temporal generative approaches over existing discriminative approaches in coping with the complexity of human daily life activities.

Volumetric differences suggest involvement of cerebellum and brainstem in chronic migraine

Background Chronic migraine (CM) is a disabling neurologic condition that often evolves from episodic migraine. There has been mounting evidence on the volumetric changes detected by magnetic resonance imaging (MRI) technique in migraineurs. These studies mainly focused on episodic migraine patients and less is known about the differences in CM patients. Method A total of 24 CM patients and 24 healthy control individuals (all females) were included in this study. All participants underwent neurological examination and MRI. High-resolution anatomical MRI images were processed with an automated segmentation method (FreeSurfer). White-matter abnormalities of the brain were also evaluated with the Age-Related White-Matter-Changes Scale. Results The volumes of the cerebellum and brainstem were found to be smaller in CM patients compared to healthy controls. White-matter abnormalities were also found in CM patients, specifically in the bilateral parieto-occipital areas. There was no correlation between the clinical variables and volume decrease in these regions. Conclusion CM patients showed significant volume differences in infratentorial areas and white-matter abnormalities in the posterior part of the brain. It is currently unclear whether the structural brain changes seen in migraine patients are the cause or the result of headaches. Longitudinal volumetric neuroimaging studies with larger groups, especially on the chronification of migraine, are needed to shed light on this topic.

Silent neurological involvement in biopsy-defined coeliac patients

Coeliac disease (CD) is an autoimmune disease of small intestine associated with sensitivity to gluten. The clinical manifestations are often of gastrointestinal nature, although the disease may be present asymptomatically as well. It is a chronic disease and in the absence of overt neurological involvement, extended gluten exposure may give rise to silent or subtle morphological and white-matter changes in central nervous system. The present study investigates such changes using brain volumetry and the assessment of white-matter tissue in CD patients without neurological symptoms. Seventeen CD patients without any neurological involvement were included in the study and went under neurological evaluation and anatomical MRI. Individual gray- and white-matter, and subcortical structure volumes were acquired for using automated volumetric analyses. The observed white-matter hyperintensities (WMH) evaluated using Age-Related White-Matter Changes scale. Findings show a bilateral decrease in cortical gray-matter and caudate nuclei volumes in CD compared to controls. Negative correlations were found between the duration of the disease and the volumes of the affected regions. Cerebellum was seemingly unaffected. In addition, significantly higher proportion of WMH was found in CD patients, specifically in bilateral frontal and occipitoparietal cortices. We observed a significant gray-matter and caudate nucleus atrophy in the CD patients in the absence of marked neurological symptoms. Present findings point out to a need for histopathological investigations potentially focusing on anti-TG2 antibodies, and serial volumetric analyses on the CD-related cortical and subcortical changes.

The neural dynamics of visual processing in monkey extrastriate cortex: a comparison between univariate and multivariate techniques

Understanding the brain mechanisms underlying invariant visual recognition has remained a central tenet of cognitive neuroscience. Much of our current understanding of this process is based on knowledge gained from visual areas studied individually. Previous electrophysiology studies have emphasized the role of the ventral stream of the visual cortex in shape processing and, in particular, of higher level visual areas in encoding abstract category information. Surprisingly, relatively little is known about the precise dynamics of visual processing along the ventral stream of the visual cortex. Here we recorded intracranial field potentials (IFPs) from multiple intermediate areas of the ventral stream of the visual cortex in two behaving monkeys engaged in a rapid face categorization task. Using multivariate pattern analysis (MVPA) techniques, we quantified at millisecond precision the face category information conveyed by IFPs in areas of the ventral stream. We further investigate the relationship between the selectivity and latency of individual electrodes as estimated with classical univariate vs. multivariate techniques and conclude on the similarity and differences between the two approaches.

Differentiating symptomatic Parkin mutations carriers from patients with idiopathic Parkinson’s disease: Contribution of automated segmentation neuroimaging method

BACKGROUND Parkin (PARK2) gene mutations are the predominant cause of autosomal recessive parkinsonism. Characteristic features include: early onset symptoms with slow clinical course, good response to low doses of levodopa, and frequently treatment-induced dyskinesia. Studies using a voxel-based morphometry approach showed a decrease in the gray matter volume of the basal ganglia in mutation carriers during the symptomatic stages. A bilateral, presumably compensatory increase of basal ganglia gray matter value was recently demonstrated in asymptomatic Parkin mutation carriers. Behavioral disorders including: anxiety, psychosis, panic attacks, depression, disturbed sexual, behavioral and obsessive-compulsive disorders have been reported in these patients. METHOD A total of 28 Parkinsons Disease (PD) patients consisting of 10 Young-Onset without Parkin mutations (YOPD), 9 Young-Onset with Parkin mutations (YOPD-p), 9 Late-Onset without Parkin mutations (LOPD) and 32 healthy control subjects were studied with an automated volumetric assessment method to quantify subcortical atrophy. Patients but not controls also underwent a neuropsychological and neuropsychiatric assessment. RESULTS Results revealed a reduction of bilateral caudate nuclei volumes in YOPD-p patients compared to the YOPD patients while there were no statistically significant differences between other groups. YOPD-p patients showed similar results to other patient groups on neuropsychiatric and neuropsychological evaluation measures. CONCLUSION YOPD-p and YOPD patients showed a different pattern of volume changes in basal ganglia. Despite its relatively benign clinical course, carrying the Parkin mutation seems to be associated with greater atrophy in subcortical structures. Failure of compensatory mechanisms, different mutation types and pathophysiologic processes may underlie this diverse pattern of subcortical brain changes.

Cognitive and anatomical correlates of anosognosia in amnestic mild cognitive impairment and early-stage Alzheimer's disease.

BACKGROUND Anosognosia is a common feature in Alzheimers disease (AD). The brain substrates of anosognosia are not fully understood, and less is known about the cognitive substrates of anosognosia in prodromal and early stages of AD. METHODS Fourty-seven patients with amnestic-type mild cognitive impairment (aMCI) (n = 26) and early-stage AD (n = 21) were included, and Clinical Insight Rating Scale and Anosognosia Questionnaire for Dementia (AQ-D) were used to assess anosognosia. A detailed neuropsychological battery was administered; each patient underwent a structural magnetic resonance imaging (MRI). Correlation between anosognosia and performance in individual cognitive domains as well as correlation between anosognosia and cortical thickness values in regions of interest were assessed. RESULTS Performance of the anosognosic patients in Digit Ordering Test (DOT), Digit Span Backwards, and Clock Drawing Test (CDT) was significantly worse compared to non-anosognosic patients in the total study population and in the aMCI subgroup but not in AD group. AQ-D scores negatively correlated with Mini-Mental State Examination (MMSE), California Verbal Learning Test (CVLT), Digit Span Backwards and CDT scores in total group and MMSE, CVLT, DOT, and Digit Span Backwards scores in the aMCI group. No significant correlations were found between cortical thickness measurements and AQ-D scores in any of the patient populations. CONCLUSIONS Anosognosia was associated with episodic memory, working memory, and executive functions in the total population and aMCI group, but no association was found in early-stage AD patients. Anosognosia in the early stages of AD may be related with non-structural changes such as hypoconnectivity rather than structural changes.

The neural basis of rapid visual recognition: Neural decoding and Granger causality analysis of connectivity

A visual paradigm that has been extensively used to study visual cognition is the rapid categorization paradigm (Thorpe et al., 1996). While much is known about its psychophysical basis, its neural underpinnings still remain to be understood. Here we recorded intracranial field potentials (IFPs) from the occipital and temporal lobes of human patients implanted with subdural electrodes while they were engaged in a rapid animal categorization task. Using multivariate pattern analysis techniques, we quantified at millisecond precision the amount of visual category information conveyed by IFPs. Our analysis, which suggests that abstract category information can be read-out at a level close to behavioral performance (typically within the 70–80% accuracy range), includes the estimated flow of visual information and a lower bound of the read-out latencies. Additional results using spectral properties of the signal suggest a substantial amount of task relevant information in the delta phase and alpha amplitude that is seen selectively in the regions along the ventral stream. By quantifying the information content using the neural decoding, we investigated the relationship between electrode selectivity to category and behavioral measures in a correlation analysis. We also employed Granger causality as a measure of connectivity during the task. This measure combined with multivariate autoregressive models was used to explain the causal interactions between the recording sites by means of revealing how a past state of a brain region informs the current state of another. Partial causality and spectral causality measures were also used over successive time windows during the task. Linking causal flow along the ventral stream to the neural information content in recording sites, we outline a comprehensive analysis of the connectivity in relation to the visual categorization and the dynamics of re-entrant signals in the low to intermediate parts of the visual system.