Conditioning of the alpha block to a tone was administered to two groups of 18 normal and 18 retarded children in order to compare their difference in condition. ability. In addition, the relationship between the number of conditioning trials and the strength of conditioning was studied. The retarded children had a mean IQ of 67.27 with an SD of 7.95. Their mean CA was 142 months with an SD of 20. The normals had a mean CA of 138 months with an SD of 15.
The CS was a tone (1000 cps. 60 db, through earphones) lasting 3 seconds, and the UCS was a light of 6W and 2-seconds duration just above eye level one meter away. Both CS and UCS were controlled by electronic timers with an interval of one second between them. The alpha rhythm was recorded by an eight-channel OFFNER TYPE T EEG. The electrodes were mounted on the central, parietal, occipital and posterior-temporal regions with bipolar technique. The rest of the two channels were used to record the stimulus presentations.
Analyses of the ratios of the mean alpha amplitude on each of three test trials (CR1, CR2, CR3) to that on the control trial (tone alone) ad the number of CRs revealed the following: (1) Retarded children were conditioned not so well as normal children in terms of the ratio of suppression of the alpha amplitude (P＜0.01).
(2) The strength of conditioning in terms of the numbers of CRs and anticipatory responses was lower in the retarded children than in the normals. (3) Further analysis of the main effect (conditioning trials) reveals that the number of conditioning trials was inversely related to the strength, of conditioning for both normal and retarded children.
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Conditioning of the Alpha Block in Normal and Mentally Retarded Children
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