Auditory information processing

Deary IJ 1999 Intelligence and visual and auditory information processing. In Ackerman PL, Kyllonen PC, Roberts RD (eds) Learning and individual differences process, trait, and content determinants. American Psychological Association, Washington, DC, p 111—133... 

Far less muscle control than normal Vomiting may occur (unless this level is reached slowly or a person has developed a tolerance for alcohol) Maior loss of balance Substantial impairment in vehicle control, attention to driving task, and in necessary visual and auditory information processing... 

Named for the bones of the cranium under which they lie, the lobes are conspicuously defined by prominent sulci of the cortex, which have a relatively constant position in human brains. Each lobe is specialized for different activities (see Figure 6.3). Located in the anterior portions of the hemispheres, the frontal lobes are responsible for voluntary motor activity, speaking ability, and higher intellectual activities. The parietal lobes, which are posterior to the frontal lobes, process and integrate sensory information. The occipital lobes, located in the posterior-most aspects of the cerebrum, process visual information, and the temporal lobes, located laterally, process auditory information. 

The nature of the signal processing, and its potential effectiveness, depends on the characteristics of the auditory system. The ear transforms the incoming acoustic signal into mechanical motion, and this motion ultimately triggers neural pulses that carry the auditory information to the brain. The essential components of the ear are shown in Fig 6.1. 

Schall U, Catts SV, Karayanidis F, Ward PB. 1999. Auditory event-related potential indices of fronto-temporal information processing in schizophrenia syndromes valid outcome prediction of clozapine therapy in a three-year follow-up. Int J Neuropsychopharmcol 2 83-93. 

As well as hallucinations and delusions, schizophrenia is characterized by deficits in information processing. Schizophrenics have difficulty suppressing irrelevant environmental stimuli. This is referred to as sensory gating or prepulse inhibition, and commonly measured with auditory evoked potentials. When two stimuli, such as sounds, are presented within 30-500 msec, the response to the second stimulus rapidly decreases upon repeated presentations in healthy people, but not in persons with schizophrenia (Braff et al., 2001). This deficit is found in family members of patients with schizophrenia, and has been linked to the alpha-7 nicotinic receptor gene. The deficit is reversed by nicotine on an acute basis, and by some antipsychotic drugs. Alpha-7 nicotinic agonists are under development as treatment for schizophrenia (Martin et al., 2004). 

An increase in theta and beta (particularly beta-2) activity and a decrease in alpha activity was found on Hypericum treatment. This electrical pattern is typical for antidepressant drugs [227]. Simultaneously, the latencies of visually and auditory evoked potentials between 100 ms and 190 ms decreased, indicating a more rapid general information processing. These effects reached their maximum at 4 weeks and remained stable during the last two weeks. 

At the final stage of information processing (response execution), the responses chosen in the previous stages are executed. A response can be any kind of action, such as eye or head movements, hand or leg movement, and verbal responses. Attention resources are also required at this stage because intrinsic (e.g., kinesthetic) and/or extrinsic feedback (e.g., visual, auditory) can be used to monitor the consequences of the actions performed. 

Human hearing arises from airborne waves alternating 50 to 20,000 times a second about the mean atmospheric pressure. These pressure variations induce vibrations of the tympanic membrane, movement of the middle-ear ossicles connected to it, and subsequent displacements of the fluids and tissues of the cochlea in the inner ear. Biomechanical processes in the cochlea analyze sounds to frequency-mapped vibrations along the basilar membrane, and approximately 3,500 inner hair cells modulate transmitter release and spike generation in 30,000 spiral ganghon cells whose proximal processes make up the auditory nerve. This neural activity enters the central auditory system and reflects sound patterns as temporal and spatial spike patterns. The nerve branches and synapses extensively in the cochlear nuclei, the first of the central auditory nuclei. Subsequent brainstem nuclei pass auditory information to the medial geniculate and auditory cortex (AC) of the thalamocortical system. 

The human auditory system processes information primarily serially having at best two receptive channels, spatial information must be built up by integration over time. This later capability, however, is profound. Out of a full orchestra, a seasoned conductor can pinpoint an errant violinist by sound alone. 

Effects on visual performance. The information processing demands of driving are mostly in the processing of visual information. In contrast the demands of a cell phone - except for the manipulation involved in dialing and answering — are mostly in processing auditory information. Nonetheless, as discussed above, when the demands imposed by the two tasks are high, interference can and does occur between the two sources. 

Generally, a BCI experiment uses visual cues and auditory cues. A visual cue tjipicaUy is a graphical symbol and/or directional signs for motor imagery. Auditory cues use sound effects instead of a visual cue. These methods evaluate the brain s information process performance. In a preliminary study, the classification accuracy was tested using visual cues and auditory cues. In this study, visual cues and auditory cues were combined and simultaneously presented. Thus, the subject trained using a combined cue. This method tested the performance between an individual cue and a combined cue [3]. 

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