Role of the parahippocampal cortex in memory for the configuration but not the identity of objects: converging evidence from patients with selective thermal lesions and fMRI.
The parahippocampal cortex and hippocampus are brain structures known to be involved in memory. However, the unique contribution of the parahippocampal cortex remains unclear. The current study investigates memory for object identity and memory of the configuration of objects in patients with small thermo-coagulation lesions to the hippocampus or the parahippocampal cortex. Results showed that in contrast to control participants and patients with damage to the hippocampus leaving the parahippocampal cortex intact, patients with lesions that included the right parahippocampal cortex (RPH) were severely impaired on a task that required learning the spatial configuration of objects on a computer screen; these patients, however, were not impaired at learning the identity of objects. Conversely, we found that patients with lesions to the right hippocampus (RH) or left hippocampus (LH), sparing the parahippocampal cortex, performed just as well as the control participants. Furthermore, they were not impaired on the object identity task. In the functional Magnetic Resonance Imaging (fMRI) experiment, healthy young adults performed the same tasks. Consistent with the findings of the lesion study, the fMRI results showed significant activity in the RPH in the memory for the spatial configuration condition, but not memory for object identity. Furthermore, the pattern of fMRI activity measured in the baseline control conditions decreased specifically in the parahippocampal cortex as a result of the experimental task, providing evidence for task specific repetition suppression. In summary, while our previous studies demonstrated that the hippocampus is critical to the construction of a cognitive map, both the lesion and fMRI studies have shown an involvement of the RPH for learning spatial configurations of objects but not object identity, and that this takes place independent of the hippocampus.
Department of Psychiatry, Douglas Mental Health University Institute, McGill University Montreal, QC, Canada.
Véronique D
VD
Bohbot
Department of Psychology, University of Arizona Tucson, AZ, USA.
John J B
JJ
Allen
McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University Montreal, QC, Canada.
Alain
A
Dagher
Department of Experimental Psychology, Helmholtz Institute, Utrecht University Utrecht, Netherlands.
Serge O
SO
Dumoulin
McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University Montreal, QC, Canada.
Alan C
AC
Evans
Neuropsychology and Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University Montreal, QC, Canada.
Michael
M
Petrides
Department of Neurology, Hospital Na Homolce Prague, Czech Republic.
Miroslav
M
Kalina
Department of Neurology, Hospital Na Homolce Prague, Czech Republic ; Department of Neurology, First Faculty of Medicine, Charles University Prague, Czech Republic.
Katerina
K
Stepankova
Department of Psychology, University of Arizona Tucson, AZ, USA ; ARL Division of Neural Systems, Memory and Aging, University of Arizona Tucson, AZ, USA.
Lynn
L
Nadel
hippocampus; human; location; parahippocampal gyrus; spatial