TY - JOUR

T1 - Perceptual differentiation and category effects in normal object recognition

T2 - a PET study

AU - Gerlach, Christian

AU - Law, I

AU - Gade, A

AU - Paulson, O B

PY - 1999/11

Y1 - 1999/11

N2 - The purpose of the present PET study was (i) to investigate the neural correlates of object recognition, i.e. the matching of visual forms to memory, and (ii) to test the hypothesis that this process is more difficult for natural objects than for artefacts. This was done by using object decision tasks where subjects decided whether pictures represented real objects or non-objects. The object decision tasks differed in their difficulty (the degree of perceptual differentiation needed to perform them) and in the category of the real objects used (natural objects versus artefacts). A clear effect of task difficulty was found in both the behavioural and in the PET data. In the PET data, the increase in task difficulty was associated with increased regional cerebral blood flow in the posterior part of the right inferior temporal gyrus and in the anterior part of the right fusiform gyrus. This may be the neural correlate of matching visual forms to memory, and the amount of activation in these regions may correspond to the degree of perceptual differentiation required for recognition to occur. With respect to behaviour, it took significantly longer to make object decisions on natural objects than on artefacts in the difficult object decision tasks. Natural objects also recruited larger parts of the right inferior temporal and anterior fusiform gyri compared with artefacts as task difficulty increased. Differences in the amount of activation in these regions may reflect the greater perceptual differentiation required for recognizing natural objects. These findings are discussed in relation to category-specific impairments after neural damage.

AB - The purpose of the present PET study was (i) to investigate the neural correlates of object recognition, i.e. the matching of visual forms to memory, and (ii) to test the hypothesis that this process is more difficult for natural objects than for artefacts. This was done by using object decision tasks where subjects decided whether pictures represented real objects or non-objects. The object decision tasks differed in their difficulty (the degree of perceptual differentiation needed to perform them) and in the category of the real objects used (natural objects versus artefacts). A clear effect of task difficulty was found in both the behavioural and in the PET data. In the PET data, the increase in task difficulty was associated with increased regional cerebral blood flow in the posterior part of the right inferior temporal gyrus and in the anterior part of the right fusiform gyrus. This may be the neural correlate of matching visual forms to memory, and the amount of activation in these regions may correspond to the degree of perceptual differentiation required for recognition to occur. With respect to behaviour, it took significantly longer to make object decisions on natural objects than on artefacts in the difficult object decision tasks. Natural objects also recruited larger parts of the right inferior temporal and anterior fusiform gyri compared with artefacts as task difficulty increased. Differences in the amount of activation in these regions may reflect the greater perceptual differentiation required for recognizing natural objects. These findings are discussed in relation to category-specific impairments after neural damage.

KW - Adult

KW - Artifacts

KW - Brain/diagnostic imaging

KW - Cognition/physiology

KW - Discrimination, Psychological/physiology

KW - Female

KW - Humans

KW - Image Processing, Computer-Assisted

KW - Magnetic Resonance Imaging

KW - Male

KW - Memory/physiology

KW - Perception/physiology

KW - Photic Stimulation

KW - Reaction Time/physiology

KW - Tomography, Emission-Computed

U2 - 10.1093/brain/122.11.2159

DO - 10.1093/brain/122.11.2159

M3 - Journal article

C2 - 10545400

VL - 122 ( Pt 11)

SP - 2159

EP - 2170

JO - Brain

JF - Brain

SN - 0006-8950

ER -