Auditory processing

A physician friend of mine has expressed it using a neurological vocabulary "If it [the drug] delayed only the neural response to a stimulus, then pitch might have been shifted down, and yet harmony between notes should have been preserved. A variable delay related to the pitch of the stimulus would produce the disharmony but would not explain the preservation of normal relationship between single tones. It seems clear that this compound affects the auditory processing centers in the brain in a complex way which deserves further scientific study. The lack of significant toxic effects should make this compound useful for further studies."... 

Simosky JK, Stevens KE, Adler LE, Freedman R. 2003. Clozapine improves deficient inhibitory auditory processing in DBA/2 mice, via a nicotinic cholinergic mechanism. Psychopharmacology 165 386-396. 

There is evidence that dopamine may play a significant role in schizophrenia (Carlsson, 1977, 1978 Bennett, 1998). Additionally, the indirect dopamine agonist, amphetamine, produces a psychotic state in healthy individuals and exacerbates the symptoms of psychosis seen in patients with schizophrenia. As such, exposure to amphetamine is a well-characterized model of the auditory processing abnormalities common to schizophrenia and several studies have investigated the effects of amphetamine on rodent ERPs. 

Although chronic ketamine (repeated acute administration for 14 days) reportedly has no effect on the amplitude or latency of any ERP components, there does appear to be some lasting effects of chronic ketamine exposure (Maxwell et al., 2006b). In a study by Maxwell and colleagues, mice were treated with ketamine daily for 2 weeks, and then tested 1 week later. Ketamine decreased N40 amplitude, but not latency 7 days after last ketamine dose. These data indicate that chronic NMDA receptor hypofunction can lead to auditory processing deficits similar to those seen in schizophrenia patients (Maxwell et al., 2006b). 

There are individual differences in the efficiency of the early stages of visual and auditory processing that correlate significantly with mental ability test scores (for reviews see Deary Stough 1996, Deary 1999). 

Dietrich KN, Succop PA, Berger OG, et al Lead exposure and the central auditory processing abilities and cognitive development of urban children the Cincinnati lead study cohort at age 5 years. Neurotoxicol Teratol 14 51-56,1992 Dietrich KN, Berger OG, Succop PA, et al The developmental consequences of low to moderate prenatal and postnatal lead exposure intellectual attainment in the Cincinnati lead study cohort following school entry. Neurotoxicol Teratol 15 37-44,1993a... 

Visual processing (field of view) Visual perception Auditory processing Central processing and memory Effectors/output behavior (35 primitive tasks) Attention—multiple-resource theory Anthropometric models Arditi and Azueta 1992 Lubin and Bergen 1992 Remington et al. 1992 Caid et al. 1983 Baddeley and Hitch 1974 Hamilton et al. 1990 Wickens 1984 Badler et al. 1993 (28)... 

Does allow potential assessment of conduction speed of neural circuits involved in auditory processing (Roncagliolo et al., 1998)... 

Dietrich KN, Succop PA, Berger OG, Keith RW (1992) Lead exposure and the central auditory processing abilities and cognitive development of urban children the Cincinnati Lead Study cohort at age 5 years. Neurotoxicol Teratol 14 51-56. 

There is hot a great deal of consistency in the areas of functioning where deficits are reported. Needlen an ei al (1979) reported deficits in verbal performance and auditory processing, but these have not been found by other workers who have assessed the same area, and in the case of the Seashore Rhythm test, used the same test (Smith ei al, 1983 Hansen ei al, 1985). 

Results from Otto s replication study also indicated that hearing threshold, a reflection of peripheral auditory system function, increased directly with lead levels. Although hearing threshold did not vary with blood lead level in the five-year follow-up study (Otto et al, 1985), this finding bears further investigation in view of other reports suggesting impaired auditory processing in lead-exposed children (de la Burde and Choate, 1975 Needleman et al, 1979) and in fact, additional new analyses reported elsewhere in this volume by Otto and by Schwartz and Otto (1987) provide further evidence for lead-induced auditory system effects. 

Although auditory processing deficits have been associated with lead exposure in children (Perino and Emhart, 1974 Needleman et al, 1979), little evidence is available concerning the effects of lead exposure on hearing in children. Elevated hearing thresholds have been observed in several studies of lead workers (reviewed by Repko and Corum, 1979), but no systematic audiometric evaluations of lead-exposed children have been reported until recently. 

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