Early visual body processing is not modulated by top-down objectbased attention in the human brain
KIRJAVAINEN, ILKKA (2013)
KIRJAVAINEN, ILKKA
2013
Psykologia - Psychology
Yhteiskunta- ja kulttuuritieteiden yksikkö - School of Social Sciences and Humanities
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Hyväksymispäivämäärä
2013-09-06
Julkaisun pysyvä osoite on
https://urn.fi/urn:nbn:fi:uta-1-24101
https://urn.fi/urn:nbn:fi:uta-1-24101
Tiivistelmä
Human bodies are a rich source of socially relevant information. Electrophysiological and imaging studies have revealed that specialized mechanisms in the brain are used to extract social information, for example, from faces, eyes, and bodies. An event-related component called N170 has been demonstrated to reflect face and body processing, while EEG components like early posterior negativity (EPN) and late positive potential (LPP) have been shown to reflect processes of attention and memory.
In this experiment, it was tested whether top-down object-based attention modulates early visual body processing and corresponding ERPs, P1 and N170. EEG was measured from 64 channels while participants saw pictures of both clothed and nude bodies, faces, and cars and directed their top-down attention towards different stimulus categories. It was found that N170 response amplitude was not enhanced when seeing attended compared to non-attended body stimuli in the parieto-occipital channels (P3/4, PO3/4 and P5/6). Also for face processing, such modulation did not occur in the temporal channels (P7/8, TP7/8 and TP9/10). However, early attentional modulation of the P1 response amplitude occurred in the occipital channels (PO9/10, O1/2). Clear attentional modulation of the ERP components was found after 300 ms for all stimulus categories. LPP response measured from centro-parietal channels was also enhanced for attended stimuli in the time window of 300 – 700 ms.
It is concluded that the initial body and face processing are unaffected by the modulation of top-down object-based attention. Top-down attention begins to affect visual body and face processing after 300 ms post-stimulus and probably is reflected in activation of a larger cortical network related to body and face processing. Early attentional modulation in the occipital channels could reflect spatial attentional processes related to differing stimulus sizes between stimulus categories. Human visual perception is tuned to detect human bodies, and top-down attention cannot rapidly modulate this processing. This ensures that evolutively important information from other peoples’ bodies is processed fast and accurately in the human brain despite of where attention is directed at any moment.
Keywords: visual body processing, top-down, object-based, attention, ERP
In this experiment, it was tested whether top-down object-based attention modulates early visual body processing and corresponding ERPs, P1 and N170. EEG was measured from 64 channels while participants saw pictures of both clothed and nude bodies, faces, and cars and directed their top-down attention towards different stimulus categories. It was found that N170 response amplitude was not enhanced when seeing attended compared to non-attended body stimuli in the parieto-occipital channels (P3/4, PO3/4 and P5/6). Also for face processing, such modulation did not occur in the temporal channels (P7/8, TP7/8 and TP9/10). However, early attentional modulation of the P1 response amplitude occurred in the occipital channels (PO9/10, O1/2). Clear attentional modulation of the ERP components was found after 300 ms for all stimulus categories. LPP response measured from centro-parietal channels was also enhanced for attended stimuli in the time window of 300 – 700 ms.
It is concluded that the initial body and face processing are unaffected by the modulation of top-down object-based attention. Top-down attention begins to affect visual body and face processing after 300 ms post-stimulus and probably is reflected in activation of a larger cortical network related to body and face processing. Early attentional modulation in the occipital channels could reflect spatial attentional processes related to differing stimulus sizes between stimulus categories. Human visual perception is tuned to detect human bodies, and top-down attention cannot rapidly modulate this processing. This ensures that evolutively important information from other peoples’ bodies is processed fast and accurately in the human brain despite of where attention is directed at any moment.
Keywords: visual body processing, top-down, object-based, attention, ERP