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Broad and narrow conceptual tuning in the human frontal lobes.

Gotts SJ, Milleville SC, Bellgowan PS, Martin A - Cereb. Cortex (2010)

Bottom Line: Broad superordinate conceptual information was represented as early as extrastriate and posterior ventral temporal cortex.Separate sites within prefrontal cortex represented broad and narrow conceptual tuning, with more anterior sites tuned narrowly to close conceptual associates in a manner that was invariant to stimulus form/position and that matched independent similarity ratings of the stimuli.The combination of broad and narrow conceptual tuning within prefrontal cortex may support flexible selection, retrieval, and classification of objects at different levels of categorical abstraction.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA. gottss@mail.nih.gov

ABSTRACT
Previous work has implicated prefrontal cortices in selecting among and retrieving conceptual information stored elsewhere. However, recent neurophysiological work in monkeys suggests that prefrontal cortex may play a more direct role in representing conceptual information in a flexible context-specific manner. Here, we investigate the nature of visual object representations from perceptual to conceptual levels in an unbiased data-driven manner using a functional magnetic resonance imaging adaptation paradigm with pictures of animals. Throughout much of occipital cortex, activity was highly sensitive to changes in 2D stimulus form, consistent with tuning to form and position within retinotopic coordinates and matching an automated measure of shape similarity. Broad superordinate conceptual information was represented as early as extrastriate and posterior ventral temporal cortex. These regions were not completely invariant to form, suggesting that form similarity remains an important organizational constraint into the temporal cortex. Separate sites within prefrontal cortex represented broad and narrow conceptual tuning, with more anterior sites tuned narrowly to close conceptual associates in a manner that was invariant to stimulus form/position and that matched independent similarity ratings of the stimuli. The combination of broad and narrow conceptual tuning within prefrontal cortex may support flexible selection, retrieval, and classification of objects at different levels of categorical abstraction.

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fMRI adaptation paradigm and task. One adaptation or “anchor” animal picture was presented several times in a row (3–7 times) at a rate of once per second (picture duration = 200 ms, crosshair duration = 800 ms). Immediately following the repeated anchor picture, a single “deviant” animal picture was presented, drawn from 1 of 5 levels of conceptual distance from the anchor. Adaptation sequences were intermixed randomly with phase-scrambled baseline pictures and pictures of man-made objects. Subjects were instructed to press a response button to pictures of man-made objects but were asked to attend to all pictures.
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fig1: fMRI adaptation paradigm and task. One adaptation or “anchor” animal picture was presented several times in a row (3–7 times) at a rate of once per second (picture duration = 200 ms, crosshair duration = 800 ms). Immediately following the repeated anchor picture, a single “deviant” animal picture was presented, drawn from 1 of 5 levels of conceptual distance from the anchor. Adaptation sequences were intermixed randomly with phase-scrambled baseline pictures and pictures of man-made objects. Subjects were instructed to press a response button to pictures of man-made objects but were asked to attend to all pictures.

Mentions: In the current study, we examine the fine-grained nature of visual object representations throughout the human brain, ranging from visual stimulus form up through the level of object concepts within the domain of animals. To do this, we employ functional magnetic resonance imaging (fMRI) adaptation (Grill-Spector and Malach 2001; Naccache and Dehaene 2001), a method inspired by single-neuron recording experiments in monkeys (e.g., Baylis and Rolls 1987; Miller et al. 1991; see Desimone 1996 for review) and used previously to characterize neural tuning curves within single fMRI voxels (e.g., Piazza et al. 2004; Andresen et al. 2009). Based on a paradigm described by Piazza et al. (2004), we repeat single-animal pictures (referred to as “anchor” pictures) several times in a row over a few seconds (see Fig. 1). This is expected to result in a large temporary decrease in neural activity (i.e., adaptation) throughout the visual brain in cells that are responsive to the stimulus. Recovery from adaptation can then be measured within each fMRI voxel to a single “deviant” picture that occurs immediately after the anchor picture and shares a particular conceptual relationship with it. If the neural representations of the anchor and deviant stimuli share many cells within a voxel, as one might expect for identical or highly related objects that have many component parts or features in common, the recovered response should be relatively weak due to persistent adaptation. In contrast, if they share few cells, as one would expect for very different objects, the response should be recovered to nonadapted levels.


Broad and narrow conceptual tuning in the human frontal lobes.

Gotts SJ, Milleville SC, Bellgowan PS, Martin A - Cereb. Cortex (2010)

fMRI adaptation paradigm and task. One adaptation or “anchor” animal picture was presented several times in a row (3–7 times) at a rate of once per second (picture duration = 200 ms, crosshair duration = 800 ms). Immediately following the repeated anchor picture, a single “deviant” animal picture was presented, drawn from 1 of 5 levels of conceptual distance from the anchor. Adaptation sequences were intermixed randomly with phase-scrambled baseline pictures and pictures of man-made objects. Subjects were instructed to press a response button to pictures of man-made objects but were asked to attend to all pictures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3020586&req=5

fig1: fMRI adaptation paradigm and task. One adaptation or “anchor” animal picture was presented several times in a row (3–7 times) at a rate of once per second (picture duration = 200 ms, crosshair duration = 800 ms). Immediately following the repeated anchor picture, a single “deviant” animal picture was presented, drawn from 1 of 5 levels of conceptual distance from the anchor. Adaptation sequences were intermixed randomly with phase-scrambled baseline pictures and pictures of man-made objects. Subjects were instructed to press a response button to pictures of man-made objects but were asked to attend to all pictures.
Mentions: In the current study, we examine the fine-grained nature of visual object representations throughout the human brain, ranging from visual stimulus form up through the level of object concepts within the domain of animals. To do this, we employ functional magnetic resonance imaging (fMRI) adaptation (Grill-Spector and Malach 2001; Naccache and Dehaene 2001), a method inspired by single-neuron recording experiments in monkeys (e.g., Baylis and Rolls 1987; Miller et al. 1991; see Desimone 1996 for review) and used previously to characterize neural tuning curves within single fMRI voxels (e.g., Piazza et al. 2004; Andresen et al. 2009). Based on a paradigm described by Piazza et al. (2004), we repeat single-animal pictures (referred to as “anchor” pictures) several times in a row over a few seconds (see Fig. 1). This is expected to result in a large temporary decrease in neural activity (i.e., adaptation) throughout the visual brain in cells that are responsive to the stimulus. Recovery from adaptation can then be measured within each fMRI voxel to a single “deviant” picture that occurs immediately after the anchor picture and shares a particular conceptual relationship with it. If the neural representations of the anchor and deviant stimuli share many cells within a voxel, as one might expect for identical or highly related objects that have many component parts or features in common, the recovered response should be relatively weak due to persistent adaptation. In contrast, if they share few cells, as one would expect for very different objects, the response should be recovered to nonadapted levels.

Bottom Line: Broad superordinate conceptual information was represented as early as extrastriate and posterior ventral temporal cortex.Separate sites within prefrontal cortex represented broad and narrow conceptual tuning, with more anterior sites tuned narrowly to close conceptual associates in a manner that was invariant to stimulus form/position and that matched independent similarity ratings of the stimuli.The combination of broad and narrow conceptual tuning within prefrontal cortex may support flexible selection, retrieval, and classification of objects at different levels of categorical abstraction.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA. gottss@mail.nih.gov

ABSTRACT
Previous work has implicated prefrontal cortices in selecting among and retrieving conceptual information stored elsewhere. However, recent neurophysiological work in monkeys suggests that prefrontal cortex may play a more direct role in representing conceptual information in a flexible context-specific manner. Here, we investigate the nature of visual object representations from perceptual to conceptual levels in an unbiased data-driven manner using a functional magnetic resonance imaging adaptation paradigm with pictures of animals. Throughout much of occipital cortex, activity was highly sensitive to changes in 2D stimulus form, consistent with tuning to form and position within retinotopic coordinates and matching an automated measure of shape similarity. Broad superordinate conceptual information was represented as early as extrastriate and posterior ventral temporal cortex. These regions were not completely invariant to form, suggesting that form similarity remains an important organizational constraint into the temporal cortex. Separate sites within prefrontal cortex represented broad and narrow conceptual tuning, with more anterior sites tuned narrowly to close conceptual associates in a manner that was invariant to stimulus form/position and that matched independent similarity ratings of the stimuli. The combination of broad and narrow conceptual tuning within prefrontal cortex may support flexible selection, retrieval, and classification of objects at different levels of categorical abstraction.

Show MeSH