Further Conclusions Regarding The Influence Of Ward Meaning On The Cortical Averaged Evoked Response In Audiology

Abstract

The influence of meaning of words and meassages was studied in relation to the auditory evoked response produced by computer-averaged EEG studies.

The basic method used was the comparison of latency and amplitude of evoked response to 64-word messages played forwards to the subject, and then with each word reversed.

Several series of variations on this method were used, e.g. with alternation of ‘words forward’ and ‘words reversed', then random groups of forward and reversed words. Spoken number series were used, and varied with ‘reversed word’ patterns in a similar way.

Several methods of synchronisation of word tapes with initiation of computer-averaging were used and compared, e.g. with a short tone, and a longer tone, on the other track of a two-track tape recorder. Also a synthetic message composed of words shown on the spectrograph to have symmetrical rise and fall times was recorded and relayed to subjects in forward and reversed form.

The effect of reversal on the word message was always the same, i.e. a reduction of amplitude of evoked response, defined as the difference in microvolts between the potentials of the N₁ and P₂ waves. Latency was not affected in this way, though there was considerable inter-subject variation.

Key Words:

• Electric Response Audiometry (ERA)
• Brain potentials
• Language evoked potentials
• Contingent Negative Variation (CNV)