Edward S. Halas

Conditioned neuronal responses at various levels in conditioning paradigms

Abstract Monopolar macro-electrodes were implanted in seven chronic and thirty-six acute cats. Brain sites investigated were the medulla and mesencephalic reticular formation, diffuse thalamic system, cochlear nucleus, inferior colliculus, brachium of the inferior colliculus, medial geniculate and the auditory cortex. All cats were given classical conditioning, consisting of a tone paired with a mild electric shock to one hind paw. In addition, the chronic animals were given instrumental avoidance conditioning. The results indicate that conditioned neuronal responses developed sequentially, starting with the reticular formation and progressing upward from the cochlear nucleus to the auditory cortex. These results were statistically significant for both classical and instrumental conditioning. Control experiments for general bodily movements, alerting or arousal, and pseudoconditioning were run and the results were found to be negative.

Blood Pressure and Heat Shock Protein Expression in Response to Acute and Chronic Stress

We previously demonstrated that restraint and pharmacological agents that activate sympathetic nervous system activity induce expression of the 70-kD heat shock protein (HSP70) in major blood vessels. The magnitude and rapidity in which HSP70 is induced in the aorta suggest that it may play a salient role in the mechanical properties of vascular smooth muscle. Other investigators have reported that HSP70 inducibility is increased in genetically hypertensive animals. In this report, we have investigated the effects of acute and chronic (8-week) exposure to restraint and restraint in the presence of a randomized intermittent air jet on the development of hypertension and the induction of HSP70 in the aorta and adrenal glands of normotensive adult male Sprague-Dawley rats. Acute restraint or air jet resulted in a fivefold to sixfold increase in aortic HSP70 mRNA expression. Chronic exposure to restraint reduced the HSP70 response to acute restraint. In contrast, no adaptation of the HSP70 response to acute air jet was observed in aortas of chronically air jet-treated rats. In adrenal glands, HSP70 expression was reduced after chronic restraint and air jet, indicating that in this tissue, adaptation occurs to both stressors. There was no difference in HSP70 expression in unstressed rats that had been chronically exposed to restraint or air jet in either adrenal gland or aorta. A significant increase (P < .05) in systolic blood pressure developed in air jet-treated animals (120 +/- 3 mm Hg) but not in restrained rats (107 +/- 2 mm Hg) compared with unstressed controls (106 +/- 3 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Food motivation of rehabilitated malnourished rats: Implications for learning studies

Adult male, and female rats that had suffered either postnatal undernutrition or postnatal zinc deficiency were more highly motivated for food than normal rats. A progressive ratio schedule was used to test the rats for food motivation. All rats were deprived of food 24 h prior to testing. Each rat was tested once a week for 8 consecutive weeks. The smaller body size of the previously malnourished rats relative to their body surface area seemed to be the best explanation for their higher level of motivation.

Specificity of multiple unit activity in the sensory nuclei of cats

Abstract Multiple unit neuronal activity was recorded from several sensory and non-sensory neural systems in conscious, but paralyzed, cats. Presentation of auditory and visual stimuli resulted in neuronal responses from the appropriate auditory and visual nuclei but not from the inappropriate sensory systems or from non-sensory systems. The maximum distance that an electrode can record multiple-unit activity was about 1.0mm. Electronic interference or noise was quite low which resulted in a fairly large signal to noise ratio.

No difference in extinction behavior in planaria following various types and amounts of training

One hundred-twenty planaria were randomly divided into 12 equal groups. The experimental groups were given 0, 150, 300, and 450 trials of paired light and shock. The light control groups were given 0, 150, 300, and 450 trials of light. The pseudoconditioning groups were given 0, 150, 300, and 450 trials of unpaired light and shock. After their respective training procedures, all groups were given 25 extinction trials on 4 successive days. Analysis revealed that there was no significant difference among the groups.

Neuronal coding at subcortical auditory nuclei

Abstract Monopolar macroelectrodes were implanted in the dorsal cochlear nucleus and inferior colliculus of four chronic adult cats and the frequency of neuronal discharge was analyzed during stimulation with human voices. The data showed that the unique patterns of neuronal discharge generated by a particular word tended to be very consistent even when the word was presented by a different voice such as a female rather than a male voice. This discharge pattern was found to be highly reliable between cats. In addition, identifying characteristics of each pattern were found to be very similar at both the cochlear nucleus and at the level of the inferior colliculus. Recordings from the geniculate body or auditory cortex did not exhibit the discharge characteristics found at lower auditory nuclei. The neuronal discharge patterns elicited by a particular stimulus may represent a mechanism whereby identical verbal stimuli are recognizable even though presented by different voices with varying input frequency.

A Factor Analysis of Neuronal Responses during Habituation in Cats

Thirteen deep macroelectrodes were permanently implanted in 6 cats. Multiple unit neuronal responses were recorded from the mesencephalic and medullary reticular formation, the thalamic diffuse system, auditory cortex, subcortical auditory nuclei, thalamic specific nuclei, and the limbic system. The purpose of the study was to determine if a neural system made up of various brain structures was correlated with the process of habituation. A principal components factor analysis was computed and an invariant factor emerged for 5 of the 6 cats. The data suggested that the subcortical auditory nuclei were the primary structures within this neural system.

Changes in rat behavior due to RNA injection

Abstract Utilizing additional control and experimental groups, replication was made of a study suggesting transfer of a learned response from one rat to another through RNA injection. Evidence of such transfer was not obtained, but rats injected with RNA, whether from trained or untrained rats, made significantly more responses than those not injected with RNA. Possible explanations of these results are discussed.

Different neuronal responses in the cochlear nucleus of a cat during classical and instrumental conditioning

Multiple-unit neuronal responses were recorded from the cochlear nucleus of a cat during classical and instrumental conditioning. Results indicate that different configurations of neuronal responses occurred during classical and instrumental conditioning.

A comparison of conditioned and unconditioned neuronal responses in the inferior colliculus of cats

Multiple-unit neuronal responses were recorded from the inferior colliculus of four cats during classical and instrumental conditioning. For three cats, the CS elicited a neuronal inhibition (unconditioned response) that was not modified by various training procedures. For the fourth cat, a conditioned neuronal response was observed during instrumental, but not during classical, conditioning.