BackgroundProspective memory (PM) is one of the most important cognitive domains in everyday life. The neuronal basis of PM has been examined by a large number of neuroimaging and neuropsychological studies, and it has been suggested that several cerebral domains contribute to PM. For these activation studies, a constellation of experimental PM trials was developed and adopted to healthy subjects. In the present study, we used a widely used clinical PM assessment battery to determine the lesions attributable to PM failure, with the hypothesis that lesion-symptom analysis using diffusion tensor imaging (DTI) in subjects with diffuse axonal injury (DAI) can reveal the neuronal basis of PM in everyday life.ResultsFourteen DAI patients (age: range of 18-36, median 24) participated in this study. PM failure was scored in the range of 0-6 using three sub-tests of the Rivermead Behavioural Memory Test. The PM scores of DAI patients were in the range of 2-6 (median 4.5, inter-quartile range 2.25). The severity of axonal injury following DAI was examined using fractional anisotropy (FA), one of the DTI parameters, at voxel level in each subject. We then obtained clusters correlated with PM failure by conducting voxel-based regression analysis between FA values and PM scores. Three clusters exhibited significant positive correlation with PM score, the left parahippocampal gyrus, left inferior parietal lobe, and left anterior cingulate.ConclusionsThis is the first lesion-symptom study to reveal the neuronal basis of PM using DTI on subjects with DAI. Our findings suggest that the neuronal basis of PM is in the left parahippocampal gyrus, left inferior parietal lobe, and/or left anterior cingulate. These findings are similar to those of previous activation studies with loading experimental PM tasks.

Elderly people have lower ability for recognizing facial emotions than younger people. Previous studies showed that older adults had difficulty in recognizing anger, sadness and fear, but there were no consistent results for happiness, surprise and disgust. Most of these studies used a small number of stimuli, and tabulated the number of correct responses for facial expressions. These characteristics of the task might be the source of the discrepancy in the findings. The present study used a task which measures participantsʼ discrimination thresholds for six basic emotions using psychophysical measurement methods. The results showed that the thresholds for elderly participants (74.8 ± 6.5 yrs) were significantly higher than for younger participants (20.1 ± 1.6 yrs) for sadness, surprise, anger, disgust and fear. There was no significant difference for happiness. Since the task that we developed was sufficiently sensitive, it is a useful tool for assessing individualsʼ ability to perceive emotion.

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