Biomedical subjects

Haline E Schendan

Publications and source records attributed to Haline E Schendan.

3 recordsLinked to original sources

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↗