Visual confrontation naming and hippocampal function - A neural network study using quantitative H-1 magnetic resonance spectroscopy

Prior research on the relationship between visual confrontation naming and hippocampal function has been inconclusive, The present study examined this relationship using quantitative H-1 magnetic resonance spectroscopy (H-1-M RS) to operationalize the function of the left and right hippocampi, The 60 -item Boston Naming Test (BNT) was used to measure naming, Our sample inclu ded 46 patients with medically intractable, focal mesial temporal lobe epil epsy who had been screened for all pathology other than mesial temporal scl erosis, Statistics included Pearson correlations and neural network analysi s (multilayer perceptron and radial basis function). Baseline BNT performan ce correlated significantly with left H-1-MRS hippocampal ratios. Thirty-si x per cent of the variance in baseline BNT performance was explained by a n eural network model using left and right H-1-MRS ratios(creatine/N-acetylas partate) as input, This was elevated to 49% when input from the right hippo campus was lesioned mathematically, In a second model, left H-1-MRS hippoca mpal ratios were modelled using measures of semantic and episodic memory as input (including the BNT), Explained variance in left H-1-MRS hippocampal ratios fell from 60.8 to 3.6% when input from BNT and another semantic memo ry measure was degraded mathematically, These results provide evidence that the speech-dominant hippocampus is a significant component of the overall neuroanatomical network of visual confrontation naming. Clinical and theore tical implications are explored.