Biomedical subjects

Christopher F Chabris

Publications and source records attributed to Christopher F Chabris.

9 recordsLinked to original sources

PubMed2006

Brain activation during semantic processing in autism spectrum disorders via functional magnetic resonance imaging.

Language and communication deficits are core features of autism spectrum disorders (ASD), even in high-functioning adults with ASD. This study investigated brain activation patterns using functional magnetic resonance imaging in right-handed adult males with ASD and a control group, matched on age, handedness, and verbal IQ. Semantic processing in the controls produced robust activation in Broca's area (left inferior frontal gyrus) and in superior medial frontal gyrus and right cerebellum. The ASD group had substantially reduced Broca's activation, but increased left temporal (Wernicke's) activation. Furthermore, the ASD group showed diminished activation differences between concrete and abstract words, consistent with behavioral studies. The current study suggests Broca's area is a region of abnormal neurodevelopment in ASD, which may be linked with semantic and related language deficits frequently observed in ASD.

Adult↗

PubMed2006

Sex differences in intellectual performance: analysis of a large cohort of competitive chess players.

Only 1% of the world's chess grandmasters are women. This underrepresentation is unlikely to be caused by discrimination, because chess ratings objectively reflect competitive results. Using data on the ratings of more than 250,000 tournament players over 13 years, we investigated several potential explanations for the male domination of elite chess. We found that (a) the ratings of men are higher on average than those of women, but no more variable; (b) matched boys and girls improve and drop out at equal rates, but boys begin chess competition in greater numbers and at higher performance levels than girls; and (c) in locales where at least 50% of the new young players are girls, their initial ratings are not lower than those of boys. We conclude that the greater number of men at the highest levels in chess can be explained by the greater number of boys who enter chess at the lowest levels.

Adolescent↗

PubMed2004

Early visual cortex organization in autism: an fMRI study.

Autism is a neurodevelopmental disorder characterized by preserved visual abilities as well as a special profile for visual cognition. We examined the visual cortex of high-ability individuals with autism in order to assess whether the presence of abnormalities at the primary sensory level in autism could be the basis of their unusual pattern of visual cognitive abilities. We found that the early sensory visual areas are normally organized in individuals with autism, with a normal ratio between central versus peripheral visual field representation. We conclude that the differences observed in the visual capacities of individuals with autism are likely to arise from higher-level cognitive areas and functions, and are the result of top-down processes.

Adolescent↗

PubMed2004

Activation of the fusiform gyrus when individuals with autism spectrum disorder view faces.

Prior imaging studies have failed to show activation of the fusiform gyrus in response to emotionally neutral faces in individuals with autism spectrum disorder (ASD) [Critchley et al., Brain 124 (2001) 2059; Schultz et al., Arch. Gen. Psychiatry 57 (2000) 331]. However, individuals with ASD do not typically exhibit the striking behavioral deficits that might be expected to result from fusiform gyrus damage, such as those seen in prosopagnosia, and their deficits appear to extend well beyond face identification to include a wide range of impairments in social perceptual processing. In this study, our goal was to further assess the question of whether individuals with ASD have abnormal fusiform gyrus activation to faces. We used high-field (3 T) functional magnetic resonance imaging to study face perception in 11 adult individuals with autism spectrum disorder (ASD) and 10 normal controls. We used face stimuli, object stimuli, and sensory control stimuli (Fourier scrambled versions of the face and object stimuli) containing a fixation point in the center to ensure that participants were looking at and attending to the images as they were presented. We found that individuals with ASD activated the fusiform face area and other brain areas normally involved in face processing when they viewed faces as compared to non-face stimuli. These data indicate that the face-processing deficits encountered in ASD are not due to a simple dysfunction of the fusiform area, but to more complex anomalies in the distributed network of brain areas involved in social perception and cognition.

Adult↗

PubMed2004

The relationship of male testosterone to components of mental rotation.

Studies suggest that higher levels of testosterone (T) in males contribute to their advantage over females in tests of spatial ability. However, the mechanisms that underlie the effects of T on spatial ability are not understood. We investigated the relationship of salivary T in men to performance on a computerized version of the mental rotation task (MRT) developed by [Science 171 (3972) (1971) 701]. We studied whether T is associated specifically with the ability to mentally rotate objects or with other aspects of the task. We collected hormonal and cognitive data from 27 college-age men on 2 days of testing. Subjects evaluated whether two block objects presented at different orientations were the same or different. We recorded each subject's mean response time (RT) and error rate (ER) and computed the slopes and intercepts of the functions relating performance to angular disparity. T level was negatively correlated with ER and RT; these effects arose from correlations with the intercepts but not the slopes of the rotation functions. These results suggest that T may facilitate male performance on MRTs by affecting cognitive processes unrelated to changing the orientation of imagined objects; including encoding stimuli, initiating the transformation processes, making a comparison and decision, or producing a response.

Adult↗

PubMed2003

Neural mechanisms of general fluid intelligence.

We used an individual-differences approach to test whether general fluid intelligence (gF) is mediated by brain regions that support attentional (executive) control, including subregions of the prefrontal cortex. Forty-eight participants first completed a standard measure of gF (Raven's Advanced Progressive Matrices). They then performed verbal and nonverbal versions of a challenging working-memory task (three-back) while their brain activity was measured using functional magnetic resonance imaging (fMRI). Trials within the three-back task varied greatly in the demand for attentional control because of differences in trial-to-trial interference. On high-interference trials specifically, participants with higher gF were more accurate and had greater event-related neural activity in several brain regions. Multiple regression analyses indicated that lateral prefrontal and parietal regions may mediate the relation between ability (gF) and performance (accuracy despite interference), providing constraints on the neural mechanisms that support gF.

Adolescent↗

PubMed2002

Evidence for preserved representations in change blindness.

People often fail to detect large changes to scenes, provided that the changes occur during a visual disruption. This phenomenon, known as "change blindness," occurs both in the laboratory and in real-world situations in which changes occur unexpectedly. The pervasiveness of the inability to detect changes is consistent with the theoretical notion that we internally represent relatively little information from our visual world from one glance at a scene to the next. However, evidence for change blindness does not necessarily imply the absence of such a representation---people could also miss changes if they fail to compare an existing representation of the pre-change scene to the post-change scene. In three experiments, we show that people often do have a representation of some aspects of the pre-change scene even when they fail to report the change. And, in fact, they appear to "discover" this memory and can explicitly report details of a changed object in response to probing questions. The results of these real-world change detection studies are discussed in the context of broader claims about change blindness.

Attention↗

PubMed2002

Cocaine-primed craving and its relationship to depressive symptomatology in individuals with cocaine dependence.

Several lines of evidence suggest a link between cocaine-primed craving and depressive symptomatology. The purpose of this study was to directly relate these two clinical phenomena. Thirty-three cocaine-dependent subjects were rated on the Hamilton Rating Scale for Depression (HRSD) at baseline and then administered an i.v. bolus of cocaine (0.2 mg/kg). Multiple regression analysis revealed that only the HRSD score was an independent predictor of cocaine-primed craving (F= 4.09; d.f. = 10,22; r = 0.81, p < 0.003) when baseline spontaneous craving during early withdrawal, age, gender, frequency of use, time since last use, monetary expenditure on cocaine and the Addiction Severity Index Drug Composite Scores were considered. These data support the hypothesis that depressive symptomatology affects cocaine-primed craving and that this relationship is relatively specific to symptoms defined by the HRSD and is not seen with a number of other clinical and demographic variables.

Adult↗

PubMed2002

Memory for centrally attended changing objects in an incidental real-world change detection paradigm.

People often have difficulty detecting visual changes in scenes, a phenomenon referred to as 'change blindness'. Although change blindness is usually observed in pictures of objects that are not the focus of attention, it also occurs for attended objects in the real world. Here, we further explore the finding that many participants fail to detect the unexpected substitution of one conversation partner for another. We show that change blindness for a conversation partner occurs in a variety of situations. Furthermore, when tested with a photographic lineup following the change, participants who noticed the substitution showed better memory for both pre- and post-change experimenters than participants who did not detect the change. We conclude that change blindness in this case is associated with relatively ineffective or inaccessible representations of previously attended objects, and we contrast these results with others indicating that change blindness arises from a failure to compare the original and changed object.

Adolescent↗