Behavioral and neurofunctional changes over time in healthy and aphasic subjects: a PET Language Activation Study

Follow-up neuroimaging studies of aphasia never addressed a comparison between aphasic and healthy subjects. Investigation of changes over time in healthy subjects during language tasks seems a prerequisite before interpretation of longitudinal changes in aphasic patients.

Six healthy subjects and 8 aphasic patients were PET scanned twice (PET1 and PET2) at a 1-year interval during a word generation task. Using SPM99, language-rest main effect was compared at PET1 and PET2 in each group, whereas group effect was assessed at each session. Correlations were analyzed in each group between performance indexes and changes in regional cerebral flood flow (rCBF) between the 2 sessions.

Language performances were improved in both groups. rCBF decreased from PET1 to PET2 in the healthy group and increased in the aphasic group in perisylvian regions bilaterally. Correlations between performance and rCBF changes across sessions were similar in the 2 groups; positive correlations involved superior temporal cortexes bilaterally, and negative correlations concerned superior frontal and medial temporal regions.

Increased perisylvian activation over time probably reflects improved performance at the expenses of cognitive effort in aphasic patients. Decreased activation in different neural systems suggests a familiarization effect with reduced emotional load.