Retinal ganglion cell dysfunction in humans following post-geniculate lesions: specific spatio–temporal losses revealed by pattern ERG

AbstractNasal and temporal hemifield (14×24°) pattern electroretinograms (PERGs) were recorded in eight patients (age range: 21–72 years) suffering from different post-geniculate lesions (documented by CT scan and/or MRI of the brain) and homonymous hemianopia at visual field testing. In total eight age-matched normal subjects served as controls. PERGs were elicited by alternating, sinusoidal gratings (90% contrast), whose spatial and temporal characteristics, 6 Hz–5 c deg−1 and 15 Hz–0.58 c deg−1, were chosen to enhance the relative contributions of parvo- (P) and magno- (M) retinal ganglion cell (GC) subsystems, respectively. Amplitudes and phases of the Fourier analyzed PERG 2nd harmonics were measured. In normal subjects, PERG amplitudes to 15 Hz–0.58 c deg−1, but not those of the 6 Hz–5 c deg−1 stimuli were on average larger (P<0.05) in nasal than in temporal hemiretinae. In hemianopic patients, PERG amplitudes of 6 Hz–5 c deg−1 stimuli were on average reduced (P<0.05) in the hemiretinae corresponding to blind hemifields, in comparison to those in the hemiretinae corresponding to functional hemifields. No differences between hemiretinae were observed for responses of the 15 Hz–0.58 c deg−1 stimuli. In both normal subjects and patients, average PERG phases did not differ between hemiretinae, while changing significantly (P