Contribution of medial versus lateral temporal-lobe structures to human odour identification

Abstract

To investigate possible distinct contributions of different temporal-lobe structures to odour identification, the University of Pennsylvania Smell Identification Test was administered monorhinally to seizure-free patients who had undergone one of three types of temporal-lobe resection practised in three different institutions for surgical treatment of epilepsy. The resections were neocorticectomy (Dublin), selective amygdalohippocampectomy (Zurich), or anterior temporal-lobe resection with encroachment on amygdala and hippocampus (Montreal). Resections, analysed from MRI scans, showed unexpected encroachment on medial structures in most patients of the neocorticectomy groups, and largest amygdala and hippocampal resections in the amygdalohippocampectomy groups. Impaired odour identification was observed in all patient groups, irrespective of surgical approach, with greatest impairment in the nostril ipsilateral to the resection. The finding of deficits in all three surgical groups suggests that damage in the anterior temporal area, perhaps in piriform cortex, is sufficient to disrupt performance on this task; it may be that function is disrupted in the medial temporal-lobe region by disconnection when the periamygdaloid area is damaged, even when amygdala and hippocampus are left intact. An alternative explanation for our results is that damage in any one of these areas disrupts a complex network involving several distinct temporal-lobe structures.

Odour identification in frontotemporal lobar degeneration

“…A preferential role for the right hemisphere in both the perceptual and semantic analysis of odours is supported by functional imaging evidence in normal subjects [9,12], and psychophysical evidence in normal subjects [28] and in patients with focal cerebral resections [15,17]. However, other evidence [7,10,11,13,18] argues against a simple serial transfer of olfactory information within or between hemispheres.…”

“…FTLD is both pathologically and clinically heterogeneous [2][3][4][5][6]. Diseases in the FTLD spectrum involve cortical areas that have been implicated in olfactory processing in functional imaging studies of healthy subjects [7][8][9][10][11][12][13][14] and in human lesion studies [15][16][17][18]. Deficits of olfactory processing have been described in a number of common neurodegenerative conditions, including idiopathic Parkinson's disease and Alzheimer's disease [7,8].…”

Projections from the periamygdaloid cortex to the amygdaloid complex, the hippocampal formation, and the parahippocampal region: A PHA‐L study in the rat

“…The detailed topography of these pathways has, however, largely remained unexplored, which probably relates to difficulties in limiting the spread of tracer injections within the borders of the periamygdaloid cortex. Also, the heterogeneity of the cytoarchitectonic and chemoarchitectonic characteristics as well as functions of the periamygdaloid cortex have only recently become appreciated Jones-Gotman et al, 1997;Mattila et al, 1999;Kemppainen and Pitkänen, 2000;Weismann et al, 2001). …”

Decrements in Volume of Anterior Ventromedial Temporal Lobe and Olfactory Dysfunction in Schizophrenia

“…This region includes the piriform cortex, the area that receives the bulk of the afferent inputs from the olfactory bulb and is primarily responsible for early odor perception. 48 No such relationship was found between these same PC volume measures and olfactory identification performance. This suggests that the link between PC volume reduction and impaired olfactory threshold detection sensitivity represents a specific structurefunction relationship that is disturbed in schizophrenia, rather than a nonspecific correlation reflecting global impairments.…”