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Biomedical subjects

N Kanwisher

Publications and source records attributed to N Kanwisher.

At least 19 recordsLinked to original sources
PubMed2005

Domain specificity in visual cortex.

We investigated the prevalence and specificity of category-selective regions in human visual cortex. In the broadest survey to date of category selectivity in visual cortex, 12 participants were scanned with functional magnetic resonance imaging while viewing scenes and 19 different object categories in a blocked-design experiment. As expected, we found selectivity for faces in the fusiform face area (FFA), for scenes in the parahippocampal place area (PPA), and for bodies in the extrastriate body area (EBA). In addition, we describe 3 main new findings. First, evidence for the selectivity of the FFA, PPA, and EBA was strengthened by the finding that each area responded significantly more strongly to its preferred category than to the next most effective of the remaining 19 stimulus categories tested. Second, a region in the middle temporal gyrus that has been reported to respond significantly more strongly to tools than to animals did not respond significantly more strongly to tools than to other nontool categories (such as fruits and vegetables), casting doubt on the characterization of this region as tool selective. Finally, we did not find any new regions in the occipitotemporal pathway that were strongly selective for other categories. Taken together, these results demonstrate both the strong selectivity of a small number of regions and the scarcity of such regions in visual cortex.

Adult↗
PubMed2004

A region of right posterior superior temporal sulcus responds to observed intentional actions.

Human adults and infants identify the actions of another agent based not only on its intrinsic perceptual features, but critically on the contingent relationship between its motion path and the environmental context [Trends Cogn. Sci. 7 (1995) 287; Cognition 72 (2003) 237]. Functional neuroimaging studies of the perception of agents and intentional actions, on the other hand, have mostly focussed on the perception of intrinsic cues to agency, like a face or articulated body motion (e.g. [J. Neurosci. 17 (1997) 4302; Neuroimage 8 (1998) 221; Trends Cogn. Sci. 4 (2000) 267; Nat. Neurosci. 3 (2000) 80; Neuroimage 13 (2001) 775; Proc. Natl. Acad. Sci. U.S.A. 98 (2001) 11656; Neuron 35 (2002) 1167; Neuron 34 (2002) 149, Neuroscience 15 (2003) 991; J. Neurosci. 23 (2003) 6819; Philos. Trans. R Soc. Lond. B. Biol. Sci. 358 (2003) 435]. Here we describe a region of the right posterior superior temporal sulcus that is sensitive not to articulated body motion per se, but to the relationship between the observed motion and the structure of the surrounding environment. From this and other aspects of the region's response, we hypothesize that this region is involved in the representation of observed intentional actions.

Adult↗
PubMed2004

Understanding other minds: linking developmental psychology and functional neuroimaging.

Evidence from developmental psychology suggests that understanding other minds constitutes a special domain of cognition with at least two components: an early-developing system for reasoning about goals, perceptions, and emotions, and a later-developing system for representing the contents of beliefs. Neuroimaging reinforces and elaborates upon this view by providing evidence that (a) domain-specific brain regions exist for representing belief contents, (b) these regions are apparently distinct from other regions engaged in reasoning about goals and actions (suggesting that the two developmental stages reflect the emergence of two distinct systems, rather than the elaboration of a single system), and (c) these regions are distinct from brain regions engaged in inhibitory control and in syntactic processing. The clear neural distinction between these processes is evidence that belief attribution is not dependent on either inhibitory control or syntax, but is subserved by a specialized neural system for theory of mind.

Brain↗
PubMed2003

People thinking about thinking people. The role of the temporo-parietal junction in "theory of mind".

Humans powerfully and flexibly interpret the behaviour of other people based on an understanding of their minds: that is, we use a "theory of mind." In this study we distinguish theory of mind, which represents another person's mental states, from a representation of the simple presence of another person per se. The studies reported here establish for the first time that a region in the human temporo-parietal junction (here called the TPJ-M) is involved specifically in reasoning about the contents of another person's mind. First, the TPJ-M was doubly dissociated from the nearby extrastriate body area (EBA; Downing et al., 2001). Second, the TPJ-M does not respond to false representations in non-social control stories. Third, the BOLD response in the TPJ-M bilaterally was higher when subjects read stories about a character's mental states, compared with stories that described people in physical detail, which did not differ from stories about nonhuman objects. Thus, the role of the TPJ-M in understanding other people appears to be specific to reasoning about the content of mental states.

Awareness↗
PubMed2001

A cortical area selective for visual processing of the human body.

Despite extensive evidence for regions of human visual cortex that respond selectively to faces, few studies have considered the cortical representation of the appearance of the rest of the human body. We present a series of functional magnetic resonance imaging (fMRI) studies revealing substantial evidence for a distinct cortical region in humans that responds selectively to images of the human body, as compared with a wide range of control stimuli. This region was found in the lateral occipitotemporal cortex in all subjects tested and apparently reflects a specialized neural system for the visual perception of the human body.

Animals↗
PubMed2001

Representation of perceived object shape by the human lateral occipital complex.

The human lateral occipital complex (LOC) has been implicated in object recognition, but it is unknown whether this region represents low-level image features or perceived object shape. We used an event-related functional magnetic resonance imaging adaptation paradigm in which the response to pairs of successively presented stimuli is lower when they are identical than when they are different. Adaptation across a change between the two stimuli in a pair provides evidence for a common neural representation invariant to that change. We found adaptation in the LOC when perceived shape was identical but contours differed, but not when contours were identical but perceived shape differed. These data indicate that the LOC represents not simple image features, but rather higher level shape information.

Adaptation, Physiological↗
PubMed2001

Neural events and perceptual awareness.

Neural correlates of perceptual awareness, until very recently an elusive quarry, are now almost commonplace findings. This article first describes a variety of neural correlates of perceptual awareness based on fMRI, ERPs, and single-unit recordings. It is then argued that our quest should ultimately focus not on mere correlates of awareness, but rather on the neural events that are both necessary and sufficient for perceptual awareness. Indeed, preliminary evidence suggests that although many of the neural correlates already reported may be necessary for the corresponding state of awareness, it is unlikely that they are sufficient for it. The final section considers three hypotheses concerning the possible sufficiency conditions for perceptual awareness.

Awareness↗
PubMed2001

Testing cognitive models of visual attention with fMRI and MEG.

Neuroimaging techniques can be used not only to identify the neural substrates of attention, but also to test cognitive theories of attention. Here we consider four classic questions in the psychology of visual attention: (i) Are some 'special' classes of stimuli (e.g. faces) immune to attentional modulation?; (ii) What are the information units on which attention operates?; (iii) How early in stimulus processing are attentional effects observed?; and (iv) Are common mechanisms involved in different modes of attentional selection (e.g. spatial and non-spatial selection)? We describe studies from our laboratory that illustrate the ways in which fMRI and MEG can provide key evidence in answering these questions. A central methodological theme in many of our fMRI studies is the use of analyses in which the activity in certain functionally-defined regions of interest (ROIs) is used to test specific cognitive hypotheses. An analogous sensor-of-interest (SOI) approach is applied to MEG. Our results include: evidence for the modulation of face representations by attention; confirmation of the independent contributions of object-based and location-based selection; evidence for modulation of face representations by non-spatial selection within the first 170 ms of processing; and implication of the intraparietal sulcus in functions general to spatial and non-spatial visual selection.

Attention↗
PubMed2001

The lateral occipital complex and its role in object recognition.

Here we review recent findings that reveal the functional properties of extra-striate regions in the human visual cortex that are involved in the representation and perception of objects. We characterize both the invariant and non-invariant properties of these regions and we discuss the correlation between activation of these regions and recognition. Overall, these results indicate that the lateral occipital complex plays an important role in human object recognition.

Brain Mapping↗
PubMed2001

The midstream order deficit.

The relative order of an auditory sequence can be more difficult to apprehend when it is presented repeatedly without pause (i.e., cycling) than when it is presented only once (Warren, Obusek, Farmer, & Warren, 1969). We find that this phenomenon, referred to as the midstream order deficit (MOD), can also occur with visual stimuli. The stimuli need not form separate perceptual "streams," and the effect can occur with presentation rates as slow as five items per second, even though the identification of individual letters is very accurate at this rate. However, if the first item of the sequence is visually very distinct from the preceding items, relative order reports can be as accurate in the cycling condition as in the single-presentation condition. Our results suggest that the MOD is not due to masking, attentional blink, repetition blindness, Reeves and Sperling's (1986) order illusion, memory limitations, or decision criteria. The MOD may reflect an attentional cost to the initiation of order encoding, which is distinct from the allocation of attention is required in order to detect and identify individual items. To initiate order encoding successfully, one's attention must be set for, or captured by, an initial salient event.

Adult↗
PubMed2000

Cortical regions involved in perceiving object shape.

The studies described here use functional magnetic resonance imaging to test whether common or distinct cognitive and/or neural mechanisms are involved in extracting object structure from the different image cues defining an object's shape, such as contours, shading, and monocular depth cues. We found overlapping activations in the lateral and ventral occipital cortex [known as the lateral occipital complex (LOC)] for objects defined by different visual cues (e.g., grayscale photographs and line drawings) when each was compared with its own scrambled-object control. In a second experiment we found a reduced response when objects were repeated, independent of whether they appeared in the same or a different format (i.e., grayscale images vs line drawings). A third experiment showed that activation in the LOC was no stronger for three-dimensional shapes defined by contours or monocular depth cues, such as occlusion, than for two-dimensional shapes, suggesting that these regions are not selectively involved in processing three-dimensional shape information. These results suggest that common regions in the LOC are involved in extracting and/or representing information about object structure from different image cues.

Brain Mapping↗
PubMed2000

The selectivity of the occipitotemporal M170 for faces.

Evidence from fMRI, ERPs and intracranial recordings suggests the existence of face-specific mechanisms in the primate occipitotemporal cortex. The present study used a 64-channel MEG system to monitor neural activity while normal subjects viewed a sequence of grayscale photographs of a variety of unfamiliar faces and non-face stimuli. In 14 of 15 subjects, face stimuli evoked a larger response than non-face stimuli at a latency of 160 ms after stimulus onset at bilateral occipitotemporal sensors. Inverted face stimuli elicited responses that were no different in amplitude but 13 ms later in latency than upright faces. The profile of this M170 response across stimulus conditions is largely consistent with prior results using scalp and subdural ERPs.

Acoustic Stimulation↗
PubMed2000

Visual attention: insights from brain imaging.

We are not passive recipients of the information that impinges on our retinae, but active participants in our own perceptual processes. Visual experience depends critically on attention. We select particular aspects of a visual scene for detailed analysis and control of subsequent behaviour, but ignore other aspects so completely that moments after they disappear from view we cannot report anything about them. Here we show that functional neuroimaging is revealing much more than where attention happens in the brain; it is beginning to answer some of the oldest and deepest questions about what visual attention is and how it works.

Animals↗
PubMed2000

Mental imagery of faces and places activates corresponding stiimulus-specific brain regions.

What happens in the brain when you conjure up a mental image in your mind's eye? We tested whether the particular regions of extrastriate cortex activated during mental imagery depend on the content of the image. Using functional magnetic resonance imaging (fMRRI), we demonstrated selective activation within a region of cortex specialized for face perception during mental imagery of faces, and selective activation within a place-selective cortical region during imagery of places. In a further study, we compared the activation for imagery and perception in these regions, and found greater response magnitudes for perception than for imagery of the same items. Finally, we found that it is possible to determine the content of single cognitive events from an inspection of the fMRI data from individual imagery trials. These findings strengthen evidence that imagery and perception share common processing mechanisms, and demonstrate that the specific brain regions activated during mental imagery depend on the content of the visual image.

Adult↗
PubMed2000

Activation in human MT/MST by static images with implied motion.

A still photograph of an object in motion may convey dynamic information about the position of the object immediately before and after the photograph was taken (implied motion). Medial temporal/medial superior temporal cortex (MT/MST) is one of the main brain regions engaged in the perceptual analysis of visual motion. In two experiments we examined whether MT/MST is also involved in representing implied motion from static images. We found stronger functional magnetic resonance imaging (fMRI) activation within MT/MST during viewing of static photographs with implied motion compared to viewing of photographs without implied motion. These results suggest that brain regions involved in the visual analysis of motion are also engaged in processing implied dynamic information from static images.

Cognition↗