Abstract
Introduction. Recently, we developed a memory-training paradigm based on non-visual drawing and demonstrated that the high-resolution primary visual cortex, V1, plays a role in implementing the concept of an amodal memory ‘sketchpad’ (Likova 2010, 2011). To reveal further brain regions whose role in memory retrieval emerges as a result of training, we ran a whole-brain pre/post-training analysis of the memory-related activation. Methods. The tasks were: Drawing guided solely by tactile memory (MD), tactile exploration and memorization (EM) of the complex images to be drawn, and control scribbling (S), each of 20 s duration, separated by 20 s rest-intervals. FMRI (Siemens 3T scanner) was run preceding one week of drawing training in the congenitally blind, and following a prolonged consolidation period. A fiber-optic motion-capture system recorded the drawing movements. Results and Conclusions. Before training, a functionally-unified network of hippocampal and temporal-lobe areas was strongly activated in the encoding EM task but non-responsive or even suppressed in the memory-retrieval MD task. Remarkably, this network was dramatically reorganized after training. The hippocampal region reversed its response pattern to become strongly MD-specific and non-responsive to the EM task. Moreover, a large EM-specific ventro-temporal strip segregated into a cascade of adjacent but functionally alternating regions. Coordinated with the hippocampus, a subset of this cascade transformed to become MD-specific, implying a memory-retrieval function emerging after the training. Contrasting patterns developed in the intervening regions. As expected, no response was observed in this network for the control (S) condition either pre- or post-training. The findings have multivalent implications, providing insights into the evolution of functional segregation as a result of learning and allowing us to evaluate novel hypotheses on cross-modal brain reorganization, as well as making potential contributions to advanced rehabilitation strategies.
Meeting abstract presented at VSS 2012