ERP Research

Schendan, H.E. and Kutas, M., 2003. Time Course of Processes and Representations Supporting Visual Object Identification and Memory. Journal of Cognitive Neuroscience, 15(1): 111-135.

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 undergraduates 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 ~150 ms. Multiple ERP repetition effects appeared over time. All but the latest ones were largest for same views, though 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 ms to 500-700 ms) and view transformation via mental rotation (posterior N400/P600 from 250-356 ms to 700 ms). 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 ms) characterized by a pattern of form-specificity consistent with the specific identification process or representation system to which the neural system contributes. download pdf

Schendan, H.E. and Kutas, M., 2002. Neurophysiological Evidence for Two Processing Times for Visual Object Identification. Neuropsychologia, 40(7): 931-945.

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 ~200 ms earlier with recoverable than unrecoverable parts. Successful identification is evident by ~300 ms when object parts and overall structural configuration are readily recoverable but not until ~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. download pdf

Schendan, H.E., Ganis, G., and Kutas, M., 1998. Neurophysiological Evidence for Visual Perceptual Categorization of Words and Faces within 150 ms. Psychophysiology, 35(3):240-251.

The nature and early time course of the initial processing differences between visually matched linguistic and nonlinguistic images were studied with event-related potentials (ERPs). The first effect began at 90 ms when ERPs to written words diverged from other objects, including faces. By 125 ms, ERPs to words and faces were more positive than those to other objects, effects identified with the P150. The amplitude and scalp distribution of P150s (and polarity reversed N170) to words and faces were similar. The P150 seemed to be elicited selectively by images resembling any well-learned category of visual patterns. We propose that (a) visual perceptual categorization based on long-term experience begins by 125 ms, (b) P150 amplitude varies with the cumulative experience people have discriminating among instances of specific categories of visual objects (e.g., words, faces), and (c) the P150 is a scalp reflection of letterstring and face intracranial ERPs in posterior fusiform gyrus. download pdf

Schendan, H.E., Kanwisher, N.G., and Kutas, M., 1997. Early Brain Potentials Link Repetition Blindness, Priming and Novelty Detection. Neuroreport, 8(8):1943-1948.

To study mechanisms of visual object identification in humans, event-related potentials (ERPs) were recorded during successful or unsuccessful identification of rapid, serially-presented words (unrepeated or repeated). We observed "repetition blindness" (RB): more repeated than unrepeated words were incorrectly reported. ERPs from repetition-blinded words exhibited little or none of the enhanced positivity found for correctly reported repeated words, resembling instead ERPs from any unrepeated sequence initially but only incorrectly reported unrepeated sequences later. Thus it appears that in RB an early (220 ms) neural operation that normally initiates facilitated processing from immediate repetition priming erroneously processes a repeated item as novel. This operation (possibly in basotemporal neocortex) appears to induce differential subsequent processing of novel versus repeated information. download pdf

 

fMRI Research

Schendan, H.E., Searl, M.M., Melrose, R.J., and Stern, C.E., 2003. An fMRI Study of the Role of the Medial Temporal Lobe in Implicit and Explicit Sequence Learning. Neuron, 37:1013-1025.

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. download pdf

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Schendan, H.E., Searl, M.M., Melrose, R.J., Stern, C.E. (2003). Sequence? What Sequence? – the human medial temporal lobe and sequence learning. Molecular Psychiatry, 8(11), 896-897. download pdf

Tinaz, A.S., Schendan, H.E., Schon, K., & Stern C.E. (2006). Evidence for the Importance of Basal Ganglia Output Nuclei in Semantic Event Sequencing: An fMRI Study. Brain Research, 1067(1):239-249. [published online December 14, 2005]

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. download pdf

 

Neuropsychological Research

Amick, M.A., Schendan, H.E., Ganis, G., Cronin-Golomb, A. (2006). 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. download pdf

Amick, M.A., Schendan, H.E., Cronin-Golomb, A. (2004). Body side of Parkinson’s disease motor symptom onset predicts performance on hierarchical pattern perception. International Neuropsychological Society Abstract, Vol. 32, p. 68. February 5, Baltimore, MD. view abstract