Biomedical subjects

Haline E Schendan

Publications and source records attributed to Haline E Schendan.

7 recordsLinked to original sources

PubMed2006

Fronto-striatal deficit in Parkinson's disease during semantic event sequencing.

Studies of Parkinson's disease (PD) suggest that cognitive deficits accompany the classically recognized motor symptoms, and that these cognitive deficits may result from damage to frontal-basal ganglia circuits. PD patients are impaired on ordering events and action components into coherent sequences. In this study, we examined early-stage, nondemented, medicated PD subjects and matched control subjects during a semantic event sequencing task using functional MRI (fMRI). The task required subjects to examine four pictures of meaningful events, determine the correct temporal relationship between each picture, and re-order the pictures into a coherent sequence. There were two main findings. First, we found abnormal activation within the prefrontal cortex (PFC) and the "default" network in the PD group. Distinct areas of the PFC showed both hypoactivation and hyperactivation, whereas the "default" network showed reduced levels of resting activation in PD. Secondly, we observed left caudate hyperactivation in the PD group. The findings are discussed in relationship to how more activation may be compensatory, but does not necessarily mean efficient and correlated brain function.

Brain Mapping↗

PubMed2006

Neuroimaging evidence for object model verification theory: Role of prefrontal control in visual object categorization.

Although the visual system rapidly categorizes objects seen under optimal viewing conditions, the categorization of objects seen under impoverished viewing conditions not only requires more time but may also depend more on top-down processing, as hypothesized by object model verification theory. Two studies, one with functional magnetic resonance imaging (fMRI) and one behavioral with the same stimuli, tested this hypothesis. FMRI data were acquired while people categorized more impoverished (MI) and less impoverished (LI) line drawings of objects. FMRI results revealed stronger activation during the MI than LI condition in brain regions involved in top-down control (inferior and medial prefrontal cortex, intraparietal sulcus), and in posterior, object-sensitive brain regions (ventral and dorsal occipitotemporal, and occipitoparietal cortex). The behavioral study indicated that taxing visuospatial working memory, a key component of top-down control processes during visual tasks, interferes more with the categorization of MI stimuli (but not LI stimuli) than does taxing verbal working memory. Together, these findings provide evidence for object model verification theory and implicate greater prefrontal cortex involvement in top-down control of posterior visual processes during the categorization of more impoverished images of objects.

Adult↗

PubMed2005

Evidence for the importance of basal ganglia output nuclei in semantic event sequencing: an fMRI study.

Semantic event sequencing is the ability to plan ahead and order meaningful events chronologically. To investigate the neural systems supporting this ability, an fMRI picture sequencing task was developed. Participants sequenced a series of four pictures presented in random order based on the temporal relationship among them. A control object discrimination task was designed to be comparable to the sequencing task regarding semantic, visuospatial, and motor processing requirements but without sequencing demands. fMRI revealed significant activation in the dorsolateral prefrontal cortex and globus pallidus internal part in the picture sequencing task compared with the control task. The findings suggest that circuits involving the frontal lobe and basal ganglia output nuclei are important for picture sequencing and more generally for the sequential ordering of events. This is consistent with the idea that the basal ganglia output nuclei are critical not only for motor but also for high-level cognitive function, including behaviors involving meaningful information. We suggest that the interaction between the frontal lobes and basal ganglia output nuclei in semantic event sequencing can be generalized to include the sequential ordering of behaviors in which the selective updating of neural representations is the key computation.

Basal Ganglia↗

PubMed2005

Frontostriatal circuits are necessary for visuomotor transformation: mental rotation in Parkinson's disease.

The mental rotation of objects requires visuospatial functions mediated by the parietal lobes, whereas the mental rotation of hands also engages frontal motor-system processes. Nondemented patients with Parkinson's disease (PD), a frontostriatal disorder, were predicted to be impaired on mentally rotating hands. Side of PD motor symptom onset was investigated because the left motor cortices likely have a causal role in hand mental rotation. The prediction was that patients with right-side onset (RPD, greater left-hemisphere dysfunction) would commit more errors rotating hands than patients with left-side onset (LPD). Fifteen LPD, 12 RPD, and 13 normal control adults (NC) made same/different judgments about pairs of rotated objects or hands. There were no group differences with objects. When rotating hands, RPD, but not LPD, made more errors than the NC group. A control experiment evaluated whether visual field of presentation explained differences between PD subgroups. In the first experiment (1A), the hand to be mentally rotated was presented in the right visual field, but here (1B) it was presented in the left visual field. Only the LPD group made more errors than the NC group. The evidence suggests a double dissociation for the RPD and LPD groups between tasks differing in visual-field presentation. The findings indicate that hemifield location of a to-be-rotated hand stimulus can cause the hemispheric frontoparietal networks to be differentially engaged. Moreover, frontostriatal motor systems and the parietal lobes play a necessary role during the mental rotation of hands, which requires integrating visuospatial cognition with motor imagery.

Aged↗

PubMed2003

An FMRI study of the role of the medial temporal lobe in implicit and explicit sequence learning.

fMRI was used to investigate the neural substrates supporting implicit and explicit sequence learning, focusing especially upon the role of the medial temporal lobe. Participants performed a serial reaction time task (SRTT). For implicit learning, they were naive about a repeating pattern, whereas for explicit learning, participants memorized another repeating sequence. fMRI analyses comparing repeating versus random sequence blocks demonstrated activation of frontal, parietal, cingulate, and striatal regions implicated in previous SRTT studies. Importantly, mediotemporal lobe regions were active in both explicit and implicit SRTT learning. Moreover, the results provide evidence of a role for the hippocampus and related cortices in the formation of higher order associations under both implicit and explicit learning conditions, regardless of conscious awareness of sequence knowledge.

Hippocampus↗

PubMed2003

Time course of processes and representations supporting visual object identification and memory.

Event-related potentials (ERPs) were used to delineate the time course of activation of the processes and representations supporting visual object identification and memory. Following K. Srinivas (1993), 66 young people named objects in canonical or unusual views during study and an indirect memory test. Test views were the same or different from those at study. The first ERP repetition effect and earliest ERP format effect started at approximately 150 msec. Multiple ERP repetition effects appeared over time. All but the latest ones were largest for same views, although other aspects of their form specificity varied. Initial ERP format effects support multiple-views-plus-transformation accounts of identification and indicate the timing of processes of object model selection (frontal N350 from 148-250 to 500-700 msec) and view transformation via mental rotation (posterior N400/P600 from 250-356 to 700 msec). Thereafter, a late slow wave reflects a memory process more strongly recruited by different than same views. Overall, the ERP data demonstrate the activation of multiple memory processes over time during an indirect test, with earlier ones (within 148-400 msec) characterized by a pattern of form specificity consistent with the specific identification-related neural process or representational system supporting each memory function.

Adolescent↗

PubMed2002

Neurophysiological evidence for two processing times for visual object identification.

Event-related brain potentials (ERPs) were recorded to fragmented pictures of objects that were named correctly or were not to investigate the time course of visual object identification. The first ERP difference distinguishing identified from unidentified pictures estimates the upper limit of the time by which human brain regions have begun to activate long-term memory (LTM) representations specifying the identity of a visual object. Data from 15 young adults indicate that this time varies with the extent to which object parts are recoverable from the visual input, being approximately 200 ms earlier with recoverable than unrecoverable parts. Successful identification is evident by approximately 300 ms when object parts and overall structural configuration are readily recoverable but not until approximately 550 ms when object parts are difficult or impossible to recover (i.e. too poorly specified by the available contours to be recovered). In both cases, successful identification is associated with greater relative positivity. However, unidentified recoverable pictures are associated with an enhanced frontal negativity (N350), linked to object matching operations, not seen for non-recoverable pictures. Taken together, these results implicate two distinct processing sequences in the successful identification of visual objects.

Adult↗