Analysis of Distributed Neural System Involved in Spatial Information, Novelty, and Memory.

Introduction

Perceiving a complex visual scene and encoding it into memory involves a hierarchical distributed network of brain regions—notably the hippocampus (HIPP), parahippocampal gyrus (PHG), lingual gyrus (LNG), and inferior frontal gyrus (IFG).

Lesion and imaging studies in humans show these regions are involved in spatial information processing as well as novelty and memory encoding; however, the relative contributions of these regions of interest (ROIs) are poorly understood.

Method

We investigated regional dissociations in spatial information and novelty processing in the context of memory encoding using a 2x2 factorial design with factors Novelty (novel vs. repeated) and Stimulus (viewing scenes with rich vs. poor spatial information). Twenty normal subjects (11M/9 F, 16-30 years) viewed images during fMRI scanning.

Results

Spatial information processing show significant effects in LNG, PHG, and HIPP (not IFG). Novelty processing was stimulus-dependant in LNG and stimulus-independent in PHG, HIPP, IFG.

Conclusions

1. Compared with novelty detection and spatial information processing, memory encoding accounted for small brain activity.
   
   
2. Activation of right IFG inversely correlated with memory performance.
   
   
3. Relation between memory performance and activation was seen in the right PHG.

We hypothesize that the right IFG dysfunction at the encoding stage may be related to either greater effort by subjects with poor memory or strategically incorrect processes that interfere with correct memory encoding.

Menon V, White CD, Eliez S, Glover GH, Reiss AL. (2000). "Analysis of a Distributed Neural System Involved in Spatial Information, Novelty and Memory Processing." Hum Brain Mapp. Oct;11(2):117-29. Abstract - PDF