title: Interhemispheric transfer in normals and acallosals: latency adjusted evoked potential averaging.
abstract: Interhemispheric transfer time (IHTT) can be estimated from visual evoked potentials (EPs). Latency adjusted averaging (LAA) produces EPs which have enhanced components. LAA also provides estimates of EP latency variance and signal-to-noise ratio (S/N). LAA was tested in analysis of EP-IHTT in normal and acallosal subjects. It was hypothesized that in normals S/N and latency variance would reveal signal degradation resulting from interhemispheric transfer. LAA in normals replicated IHTT findings for both P1 and N1 latency. Latency variance did not increase for cross-callosal measures, whereas the S/N measure showed significant EP degradation due to callosal transfer. EPs from five subjects with callosal absence (two commissurotomy; two complete and one partial callosal agenesis) showed significantly larger than normal latency variability, as well as decreased S/N ratios, for cross-hemisphere visual EPs. Results support the value of LAA in EP research on adequacy of hemispheric interactions in clinical populations.
authors.affiliation: The Travis Institute for Biopsychosocial Research, Fuller Graduate School of Psychology, Dept. of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, USA.
authors.forename: W S
authors.initials: WS
authors.lastname: Brown
authors.forename: M D
authors.initials: MD
authors.lastname: Bjerke
authors.forename: G C
authors.initials: GC
authors.lastname: Galbraith
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D003337:Corpus Callosum / Q000502:physiology* / Q000503:physiopathology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology*; D013647:Task Performance and Analysis