Visuospatial short-term memory relies on a widely dis-tributed neocortical network: some areas support the encoding processof the visually acquired spatial information, whereas other ares aremore involved in the active maintenance of the encoded information.Recently, in a pointing to remembered targets task, it has been shownin healthy subjects that, for memory delays of 5 s, spatial errors areaffected also by cognitive allocentric information, i.e., covert spatialinformation derived from a pure mental representation. We tested theeffect of a lesion of the hippocampus on the accuracy of pointing move-ments toward remembered targets, with memory delays falling in the0.5–30 s range. The spatial distributions of the two target sets we used(line and left-right ) allowed the exploitation of cognitive allocentric spa-tial information: both sets were in the frontal plane, the line one beingcomposed by eleven points distributed uniformly along a virtual linetilted 458 away from the vertical, whereas the left-right set was com-posed by two workspaces symmetrically distributed at the extremes of ahorizontal virtual line. We have found a significant difference betweenthe performance of three hippocampal amnesic subjects and a group ofnormal controls for delays equal to or longer than 15 s, the differencebeing along the allocentric axis, i.e., the direction of the virtual linedefined by the target set. On this basis we suggest that the hippocampalformation may enhance the spatial information processed within short-term memory with cognitive allocentric information. The associationthat may be operated through the neocortical-hippocampal loop of thenewly acquired spatial information with well established spatial cogni-tive items could affect the precision of the short-term memory storagefor memory delays exceeding about 15 s and might be the result of amodulation of the span of the spatial memory buffer along context-spe-cific directions
Integration of cognitive allocentric information in visuospatial short-term memory through the hippocampus
Koch GSecondo
;
2005
Abstract
Visuospatial short-term memory relies on a widely dis-tributed neocortical network: some areas support the encoding processof the visually acquired spatial information, whereas other ares aremore involved in the active maintenance of the encoded information.Recently, in a pointing to remembered targets task, it has been shownin healthy subjects that, for memory delays of 5 s, spatial errors areaffected also by cognitive allocentric information, i.e., covert spatialinformation derived from a pure mental representation. We tested theeffect of a lesion of the hippocampus on the accuracy of pointing move-ments toward remembered targets, with memory delays falling in the0.5–30 s range. The spatial distributions of the two target sets we used(line and left-right ) allowed the exploitation of cognitive allocentric spa-tial information: both sets were in the frontal plane, the line one beingcomposed by eleven points distributed uniformly along a virtual linetilted 458 away from the vertical, whereas the left-right set was com-posed by two workspaces symmetrically distributed at the extremes of ahorizontal virtual line. We have found a significant difference betweenthe performance of three hippocampal amnesic subjects and a group ofnormal controls for delays equal to or longer than 15 s, the differencebeing along the allocentric axis, i.e., the direction of the virtual linedefined by the target set. On this basis we suggest that the hippocampalformation may enhance the spatial information processed within short-term memory with cognitive allocentric information. The associationthat may be operated through the neocortical-hippocampal loop of thenewly acquired spatial information with well established spatial cogni-tive items could affect the precision of the short-term memory storagefor memory delays exceeding about 15 s and might be the result of amodulation of the span of the spatial memory buffer along context-spe-cific directionsI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
