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“As do animals, humans need categories for cognition. Without the existence of such categories,
orientation in a manifold and most variegated world would not be possible. Categories allow us to
recognize invariance in a highly variable environment.
To a large extent, as humans we are free to create such categories – they reflect, among other things,
our cultural interests (e.g., categories in law or categories used in noun classification languages). […]
Nonetheless, there should be zones of overlap or a common core. It is due to phylogeny. We
categorize the observed outside world as for example individuals with intentions and roles, actions
with possible states or enunciations that have a relation to reality (thus giving rise to mood as a
grammatical category).
Partly, this common background is reflected by the ontogeny of acquiring a first language. We have to
acquire first the permanence of an object, i.e., the identity existing between seemingly different
apparitions of the same object. While this process may be associated with a projection zone of our
visual system located in the inferior temporal lobes in both hemispheres of our brain, in a later phase
we learn to recognize an identity among different objects or phenomena – that is we learn to truly
categorize. This faculty has a strong link to the anterior parts of our frontal lobes. Moreover, all
existing evidence suggests that this faculty does not only concern visible or palpable objects like birds,
stones or trees. In primates, it also extends to categorization on a more abstract level – for instance of
the intentional actions and transitive movements (grasping of an apple) already mentioned. […]”
1: Anim Cogn. 2008 Feb 8 [Epub ahead of print]
Ultra-rapid categorisation in non-human primates.
Girard P, Jouffrais C, Kirchner CH.
Université de Toulouse, CerCo, UPS, 31062, Toulouse, France, [email protected].
The visual system of primates is remarkably efficient for analysing information about objects present
in complex natural scenes. Recent work has demonstrated that they perform this at very high speeds.
In a choice saccade task, human subjects can initiate a first reliable saccadic eye movement response
to a target (the image containing an animal) in only 120 ms after image onset. Such fast responses
impose severe time constraints if one considers neuronal responses latencies in high-level ventral areas
of the macaque monkey. The question then arises: are non-human primates able to perform the task?
Two rhesus macaque monkeys (Macaca mulatta) were trained to perform the same forced-choice
categorization task as the one used in humans. Both animals performed the task with a high accuracy
and generalized to new stimuli that were introduced everyday: accuracy levels were comparable both
with new and well-known images (84% vs. 94%). More importantly, reaction times were extremely
fast (minimum reaction time 100 ms and median reaction time 152 ms). Given that typical single units
onset times in Inferotemporal cortex (IT) are about as long as the shortest behavioural responses
measured here, we conclude that visual processing involved in ultra rapid categorisations might be
based on rather simple shape cue analysis that can be achieved in areas such as extrastriate cortical
area V4. The present paper demonstrates for the first time, that rhesus macaque monkeys (Macaca
mulatta) are able to match human performance in a forced-choice saccadic categorisation task of
animals in natural scenes.
PMID: 18259787 [PubMed - as supplied by publisher]
2: Neurosci Res. 2008 May;61(1):70-8. Epub 2008 Feb 6.
Categorization of biologically significant objects, food and gender, in rhesus monkeys I.
Behavioral study.
Inoue T, Hasegawa T, Takara S, Lukáts B, Mizuno M, Aou S.
Department of Brain Sciences and Engineering, Graduate School of Life Science and Systems
Engineering, Kyushu Institute of Technology, Kitakyushu, Fukuoka 808-0196, Japan.
Macaque monkeys have a highly evolved visual system comparable to that of humans. One of the
important visual functions is performing discriminations among biologically significant objects such
as food or heterosexual partners. In the present study, we examined whether rhesus monkeys could
categorize two-dimensional images related to food or gender using a visual discrimination task. Three
rhesus monkeys were trained to make distinctions of food from non-food items, and between male and
female monkeys, using 60 or more different pictures of each category. After more than 9 months of
training, the monkeys discriminated a variety of foods from non-food and different males from
females with more than 80% accuracy, even when the stimuli were used for the first time or presented
only once in a session. The proportion of correct responses and response latencies showed better
performance in discrimination of food/non-food than that of gender. The results suggest that rhesus
monkeys are able to perform visual discrimination of highly abstract biologically significant categories
with better performance in a food-related category than a gender-related one, using two-dimensional
visual information.
PMID: 18329121 [PubMed - in process]
3: Proc Biol Sci. 2007 Sep 7;274(1622):2069-76.
Individuation and holistic processing of faces in rhesus monkeys.
Dahl CD, Logothetis NK, Hoffman KL.
Max Planck Institute for Biological Cybernetics, Tübingen 72012, Germany.
Despite considerable evidence that neural activity in monkeys reflects various aspects of face
perception, relatively little is known about monkeys' face processing abilities. Two characteristics of
face processing observed in humans are a subordinate-level entry point, here, the default recognition
of faces at the subordinate, rather than basic, level of categorization, and holistic effects, i.e.
perception of facial displays as an integrated whole. The present study used an adaptation paradigm to
test whether untrained rhesus macaques (Macaca mulatta) display these hallmarks of face processing.
In experiments 1 and 2, macaques showed greater rebound from adaptation to conspecific faces than to
other animals at the individual or subordinate level. In experiment 3, exchanging only the bottom half
of a monkey face produced greater rebound in aligned than in misaligned composites, indicating that
for normal, aligned faces, the new bottom half may have influenced the perception of the whole face.
Scan path analysis supported this assertion: during rebound, fixation to the unchanged eye region was
renewed, but only for aligned stimuli. These experiments show that macaques naturally display the
distinguishing characteristics of face processing seen in humans and provide the first clear
demonstration that holistic information guides scan paths for conspecific faces.
Publication Types:
Research Support, Non-U.S. Gov't
PMID: 17609192 [PubMed - indexed for MEDLINE]
PMCID: PMC1919404
4: J Neurophysiol. 2007 Jun;97(6):4296-309. Epub 2007 Apr 11.
Object category structure in response patterns of neuronal population in monkey inferior
temporal cortex.
Kiani R, Esteky H, Mirpour K, Tanaka K.
Research Group for Brain and Cognitive Sciences, School of Medicine, Shaheed Beheshti University,
P.O. Box 19835-181, Tehran, Iran.
Our mental representation of object categories is hierarchically organized, and our rapid and
seemingly effortless categorization ability is crucial for our daily behavior. Here, we examine
responses of a large number (>600) of neurons in monkey inferior temporal (IT) cortex with a large
number (>1,000) of natural and artificial object images. During the recordings, the monkeys
performed a passive fixation task. We found that the categorical structure of objects is represented by
the pattern of activity distributed over the cell population. Animate and inanimate objects created
distinguishable clusters in the population code. The global category of animate objects was divided
into bodies, hands, and faces. Faces were divided into primate and nonprimate faces, and the primateface group was divided into human and monkey faces. Bodies of human, birds, and four-limb animals
clustered together, whereas lower animals such as fish, reptile, and insects made another cluster. Thus
the cluster analysis showed that IT population responses reconstruct a large part of our intuitive
category structure, including the global division into animate and inanimate objects, and further
hierarchical subdivisions of animate objects. The representation of categories was distributed in
several respects, e.g., the similarity of response patterns to stimuli within a category was maintained
by both the cells that maximally responded to the category and the cells that responded weakly to the
category. These results advance our understanding of the nature of the IT neural code, suggesting an
inherently categorical representation that comprises a range of categories including the amply
investigated face category.
Publication Types:
Research Support, Non-U.S. Gov't
PMID: 17428910 [PubMed - indexed for MEDLINE]
5: J Neurophysiol. 2007 Apr;97(4):2900-16. Epub 2007 Jan 24.
Properties of shape tuning of macaque inferior temporal neurons examined using rapid serial
visual presentation.
De Baene W, Premereur E, Vogels R.
Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven Medical School, Campus Gasthuisberg,
Herestraat 49, bus 1021, Leuven, B-3000, Belgium.
We used rapid serial visual presentation (RSVP) to examine the tuning of macaque inferior temporal
cortical (IT) neurons to five sets of 25 shapes each that varied systematically along predefined shape
dimensions. A comparison of the RSVP technique using 100-ms presentations with that using a longer
duration showed that shape preference can be determined with RSVP. Using relatively complex
shapes that vary along relatively simple shape dimensions, we found that the large majority of neurons
preferred extremes of the shape configuration, extending the results of a previous study using simpler
shapes and a standard testing paradigm. A population analysis of the neuronal responses demonstrated
that, in general, IT neurons can represent the similarities among the shapes at an ordinal level,
extending a previous study that used a smaller number of shapes and a categorization task. However,
the same analysis showed that IT neurons do not faithfully represent the physical similarities among
the shapes. The responses to the two-part shapes could be predicted, virtually perfectly, from the
average of the responses to the respective two parts presented in isolation. We also showed that IT
neurons adapt to the stimulus distribution statistics. The neural shape discrimination improved when a
shape set with a narrower stimulus range was presented, suggesting that the tuning of IT neurons is not
static but adapts to the stimulus distribution statistics, at least when stimulated at a high rate with a
restricted set of stimuli.
Publication Types:
Research Support, Non-U.S. Gov't
PMID: 17251368 [PubMed - indexed for MEDLINE]
6: J Neurosci. 2006 Oct 11;26(41):10524-35.
Related Articles, Links
Neuronal responses to object images in the macaque inferotemporal cortex at different stimulus
discrimination levels.
Suzuki W, Matsumoto K, Tanaka K.
Cognitive Brain Mapping Laboratory, RIKEN Brain Science Institute, Wako, Saitama 351-0198,
Japan.
We can discriminate visual objects at multiple levels, from coarse categorization to individual
identification. It is not known how the brain adapts to the varying levels of discrimination required in
different behavioral contexts. In the present study, we investigated whether the stimulus selectivity of
neuronal responses in the monkey inferotemporal cortex, which is the final unimodal stage in the
ventral visual pathway, changes with the varying levels of discrimination required for different task
conditions. Responses of each inferotemporal cell to the same set of nine object images were
examined in two different task conditions. The task alternated between coarse and fine discriminations
in the first experiment, and the rule alternated between categorization and individual object
identification in the second experiment. Despite these changes in the task requirements and the
resulting differences in the monkeys' behavior, we found that the responses of inferotemporal cells
were largely unchanged in both experiments. Our results suggest that representation of object images
in the inferotemporal cortex is stable and rather insensitive to these kinds of shifts in behavioral
context. Neuronal adaptations to behavioral context may occur downstream of the inferotemporal
cortex.
Publication Types:
Comparative Study
Research Support, Non-U.S. Gov't
PMID: 17035537 [PubMed - indexed for MEDLINE]
7: Nature. 2006 Sep 7;443(7107):85-8. Epub 2006 Aug 27.
Related Articles, Links
Experience-dependent representation of visual categories in parietal cortex.
Freedman DJ, Assad JA.
Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston,
Massachusetts 02115, USA. [email protected]
Categorization is a process by which the brain assigns meaning to sensory stimuli. Through
experience, we learn to group stimuli into categories, such as 'chair', 'table' and 'vehicle', which are
critical for rapidly and appropriately selecting behavioural responses. Although much is known about
the neural representation of simple visual stimulus features (for example, orientation, direction and
colour), relatively little is known about how the brain learns and encodes the meaning of stimuli. We
trained monkeys to classify 360 degrees of visual motion directions into two discrete categories, and
compared neuronal activity in the lateral intraparietal (LIP) and middle temporal (MT) areas, two
interconnected brain regions known to be involved in visual motion processing. Here we show that
neurons in LIP--an area known to be centrally involved in visuo-spatial attention, motor planning and
decision-making-robustly reflect the category of motion direction as a result of learning. The activity
of LIP neurons encoded directions of motion according to their category membership, and that
encoding shifted after the monkeys were retrained to group the same stimuli into two new categories.
In contrast, neurons in area MT were strongly direction selective but carried little, if any, explicit
category information. This indicates that LIP might be an important nexus for the transformation of
visual direction selectivity to more abstract representations that encode the behavioural relevance, or
meaning, of stimuli.
Publication Types:
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
PMID: 16936716 [PubMed - indexed for MEDLINE]
Publication Types:
Research Support, Non-U.S. Gov't
PMID: 16513005 [PubMed - indexed for MEDLINE]
9: Proc Natl Acad Sci U S A. 2004 Mar 2;101(9):3184-9. Epub 2004 Feb 20.
Related Articles, Links
Categorization in the monkey hippocampus: a possible mechanism for encoding information
into memory.
Hampson RE, Pons TP, Stanford TR, Deadwyler SA.
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, WinstonSalem, NC 27157, USA.
The mammalian hippocampus processes sensory information into memory. The neurobiological basis
of this representation, as well as the type of information that is encoded, is central to understanding
how memories are formed. Normally, there is an infinite amount of information that could be encoded
for any given stimulus. Thus, the question arises as to how the hippocampus selects and encodes
features of a given stimulus. Here, we show that neurons in the hippocampus of the monkey appear to
categorize types of visual stimuli presented in a delayed-match-to-sample memory task. By extracting
unique combinations of features, these category cells are able to encode aspects of behaviorally
important images instead of encoding all visual details. The subject is then able to rapidly select an
appropriate response to that stimulus when distracting stimuli are presented simultaneously, thereby
facilitating performance. Moreover, across animals, this specific type of encoding differed
considerably. Just as in humans, different monkeys attended to and selected different aspects of the
same stimulus image, most likely reflecting different histories, strategies, and expectations residing
within individual hippocampal networks.
Publication Types:
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.
PMID: 14978264 [PubMed - indexed for MEDLINE]
PMCID: PMC365764
10: Behav Brain Res. 2004 Feb 4;149(1):1-7.
Related Articles, Links
Visual categorization and the inferior temporal cortex.
Sigala N.
MRC-Cognition and Brain Sciences Unit, 15 Chaucer Road, CB2 2EF, Cambridge, UK.
[email protected]
We investigated the effects of categorization on the representation of stimulus features in combined
psychophysical-electrophysiological experiments. We used parameterized line drawings of faces and
fish as stimuli, and we varied the relevance of the different features for the categorization task. The
psychophysical and electrophysiological data support an exemplar-based framework for visual object
recognition. We recorded from visual neurons in the anterior inferior temporal (IT) cortex of macaque
monkeys, while they were performing a categorization task. The visual neurons did not respond
selectively to one stimulus set, or to one category. The majority of the anterior IT feature selective
neurons were tuned for features that were diagnostic for the categorization task. We argue that this
fine-tuning of the neurons reflects the perceptual sensitization to the diagnostic features.
Publication Types:
Clinical Trial
Comparative Study
Research Support, Non-U.S. Gov't
PMID: 14739004 [PubMed - indexed for MEDLINE]
: J Vis. 2008 Feb 22;8(2):9.1-15.
Related Articles, Links
Object features used by humans and monkeys to identify rotated shapes.
Nielsen KJ, Logothetis NK, Rainer G.
Max Planck Institute for Biological Cybernetics, Tübingen, Germany. [email protected]
Humans and rhesus monkeys can identify shapes that have been rotated in the picture plane.
Recognition of rotated shapes can be as efficient as recognition of upright shapes. Here we investigate
whether subjects showing view-invariant performance use the same object features to identify upright
and rotated versions of a shape. We find marked differences between humans and monkeys. While
humans tend to use the same features independent of shape orientation, monkeys use unique features
for each orientation. Humans are able to generalize to a greater degree across orientation changes than
rhesus monkey observers, who tend to relearn separate problems at each orientation rather than
flexibly apply previously learned knowledge to novel problems.
Publication Types:
Comparative Study
Research Support, Non-U.S. Gov't
PMID: 18318635 [PubMed - indexed for MEDLINE]
1: Neuron. 2007 Aug 2;55(3):341-4.
Related Articles, Links
Comment on:
Neuron. 2007 Aug 2;55(3):507-20.
Appearance isn't everything: news on object representation in cortex.
Riesenhuber M.
Department of Neuroscience, Georgetown University Medical Center, Research Building Room WP12, 3970 Reservoir Road, Northwest, Washington, D.C. 20007, USA. [email protected]
How objects are represented in the visual system is one of the big questions in cognitive neuroscience.
In this issue of Neuron, Mahon and colleagues present an intriguing study that suggests that properties
of objects other than shape can influence the arrangement of object selectivities in visual areas. In the
process, the study also points to important caveats regarding the ability of standard fMRI studies to
make inferences about neuronal selectivity.
Publication Types:
Comment
Editorial
Review
PMID: 17678848 [PubMed - indexed for MEDLINE]