An auditory evoked potential study of consonant perception in different vowel environments

Auditory evoked responses (AER) to series of consonant—vowel syllables were recorded from temporal and parietal scalp locations from 20 right-handed female college students. Averaged AERs were submitted to principal components analysis and analysis of variance. Seven components of the group's AERs were found to reflect various aspects of the stimulus parameters. One component reflected changes over only the left hemisphere to different consonants independent of the following vowel sound. A second component changed systematically over both hemispheres in response to only consonant changes. A third component systematically changed for the different consonants depending on the following vowel.     

Reactivity and aggression in the rat: induction by alpha-adrenergic blocking agents injected ventral to anterior septum but not into lateral septum.

Intracranial injections were made bilaterally through permanently implanted cannulas ending in the lateral septum or in the region ventral to the anterior septum. The rats were first screened with injections of a local anesthetic, lidocaine, which blocks both synaptic and axonal conduction. Those animals that showed an increase in reactivity and aggression were then injected with a synaptic transmitter blocking agent. The results showed that transmitter blocking agents reproduced the effect of the local anesthetic only in the region ventral to the anterior septum and that alpha-adrenergic (phentolamine, tolazoline), but not beta-adrenergic (propranolol, hydralazine), cholinergic (atropine, hyocine), or dopaminergic (haloperidol) blocking agents were effective. These results suggest that synapses in the forebrain system controlling reactivity and aggression are alpha-asrenergic and are located in the region ventral to the anterior septum just lateral to the diagonal band of Broca. The septum itself may be involved only to the extent that it is traversed by fibers of passage.     

The effect of continuity on auditory stream segregation

Condition, transitions between tones were abrupt; in the “ramped” condition, successive tones were connected by frequency glides. In the “semiramped” condition, there were partial glides in frequency (as in speech). “Discrete” sequences were most likely to split perceptually into high and low streams, making order discriminations difficult. The “ramped” condition was least likely to split, and order perception was easiest. Results for the “semiramped” condition were intermediate. The discussion relates these findings to the acoustic properties of speech and to the process of auditory stream formation.