Neurocognitive mechanisms of conceptual processing in healthy adults and patients with schizophrenia☆

Abstract

This overview outlines findings of cognitive and neurocognitive studies on comprehension of verbal, pictorial, and video stimuli in healthy participants and patients with schizophrenia. We present evidence for a distinction between two complementary neurocognitive streams of conceptual analysis during comprehension. In familiar situations, adequate understanding of events may be achieved by mapping the perceived information on the associative and similarity-based connections between concepts in semantic memory -a process reflected by an N400 waveform of event-related electrophysiological potentials (ERPs). However, in less conventional contexts, a more flexible mechanism may be needed. We suggest that this alternative processing stream, reflected by a P600 ERP waveform, may use discrete, rule-like goal-related requirements of real-world actions to comprehend relationships between the perceived people, objects, and actions. This neurocognitive model of comprehension is used as a basis in discussing relevant studies in schizophrenia. These studies suggest an imbalanced engagement of the two neurocognitive streams in schizophrenia, whereby patients may rely on the associative and similarity-based networks in semantic memory even when it would be more adaptive to recruit mechanisms that draw upon goal-related requirements. Finally, we consider the roles that these conceptual mechanisms may play in real-life behavior, and the consequences that their dysfunction may have for disorganized behavior and inability to plan actions to achieve behavioral goals in schizophrenia. Imbalanced KeywordsReal-world cognition; schizophrenia; comprehension of verbal and non-verbal information; eventrelated potentials

Top-down modulation of visual processing and knowledge after 250 ms supports object constancy of category decisions

“…In contrast, the earlier N3 and later SW show knowledge effects at both impoverishment levels, though more for LI than MI, dissociating late ERPs from each other. This dissociation between the N3 and N400/P600 supports a dichotomy (Kousta et al, 2011 ) between experiential (sensorimotor, affect) knowledge, as indexed by the N3 for vision, and linguistic (verbal) knowledge, indexed by the N400, and later strategic evaluation of earlier category decision processes and secondary higher-order semantic memory analysis, indexed by the P600/LPC (Schendan and Kutas, 2002 ; Sitnikova et al, 2010 ).…”

“…Hence, the N400 will be more negative for MI than LI and for real than pseudo objects and show impoverished-real-object effects, like the N3 and P600/LPC (Table 1 ). Also, a broad slow wave (SW) starting around 700 ms has been associated with response planning for category decisions, including naming, being more positive for named than unnamed objects (Schendan and Kutas, 2002 , 2003 ; Folstein et al, 2008 ; Schendan and Lucia, 2009 ; Schendan and Maher, 2009 ; Sitnikova et al, 2010 ). This predicts greater SW positivity for LI than MI and for real than pseudo objects, but no interaction, as the SW reflects processes after the category decision.…”

Electrophysiological Potentials Reveal Cortical Mechanisms for Mental Imagery, Mental Simulation, and Grounded (Embodied) Cognition

“…The MUSI account revises this story by adding State 3 that operates after about 400 to 500 ms and performs internal evaluation and verification processes, including conscious effortful mental simulations. For example, later verification of category decisions, more complex semantic processes, and episodic memory have been associated with a posterior late positive complex (LPC) after ∼500 ms (Schendan and Kutas, 2002 ; Rugg and Curran, 2007 ; Voss et al, 2010 ) that is, instead, more positive to incongruous than congruous semantic contexts with objects, videos, and faces (Ganis et al, 1996 ; Schendan and Kutas, 2002 ; Ganis and Kutas, 2003 ; Sitnikova et al, 2009 , 2010 ). Altogether, this predicts that the N3 and N400 will be more negative and the LPC will be more positive when mental imagery does not match the current picture (incongruous) than when it does match (congruous).…”

Brain Responses at Encoding Predict Limited Verbal Memory Retrieval by Persons with Schizophrenia

“…As with the Dm component, the task approach of the individual affects LPCs. LPCs are related to planning goal-directed behaviors, which may be more useful than a semantic strategy in some tasks (Sitnikova, Perrone, Goff, & Kuperberg, 2010).…”