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PubMed1991

Failure of haloperidol to block the effects of phencyclidine and dizocilpine on prepulse inhibition of startle.

Prepulse inhibition of acoustic or tactile startle (PPI), a form of sensorimotor gating, occurs when a weak prestimulus precedes a startling stimulus and inhibits the startle response. Studies of PPI have revealed that schizophrenic patients exhibit a deficit in this form of sensorimotor gating. In rats, PPI is blocked by dopamine agonists such as apomorphine or quinpirole, effects that are antagonized by haloperidol. Phencyclidine (PCP) has been suggested as a possible model psychotogen and produces a deficit in PPI that is similar to what is observed in schizophrenic patients. Dizocilpine is an anticonvulsant drug that, like PCP, is a noncompetitive antagonist of N-methyl-D-aspartate (NMDA)-induced excitations in brain and also disrupts PPI. In the present study, PPI of acoustic and tactile startle was measured in male Sprague-Dawley rats after injections of 5.0 mg/kg PCP with or without pretreatment with 0.02 or 0.1 mg/kg haloperidol, or with 0.5 mg/kg dizocilpine with or without pretreatment with 0.1 mg/kg haloperidol. The 0.1 mg/kg dose of haloperidol blocks the effects of apomorphine or quinpirole on PPI in rats. Startle was elicited by noise bursts at 105 or 120 dB or by air-puffs (tactile) and was inhibited by 75 or 85 dB prepulse stimuli presented 100 msec before the startle stimuli. The different eliciting stimuli produced different levels of startle in both control and drug-treated animals. Both NMDA antagonists significantly reduced the amount of PPI induced by the 75 dB prestimulus, independently of the level of startle responses elicited by the startle stimuli. Haloperidol did not block the disruption of PPI induced by either PCP or dizocilpine. In addition, PCP was unable to block PPI when the 85 rather than the 75 dB prepulse was used to inhibit either acoustic or tactile startle. These results confirm that putative NMDA antagonists inhibit sensorimotor gating in rats and suggest that these effects are not mediated by the activation of central dopamine systems.

Animals↗
PubMed1991

Auditory event-related potentials and electrodermal activity in medicated and unmedicated schizophrenics.

Event-related potentials (ERPs) and electrodermal activity were studied in 14 medicated schizophrenics, 17 unmedicated schizophrenics, and 23 age- and education-matched controls. Subjects were run in three auditory stimulus paradigms differing from the usual ERP paradigms in having interstimulus intervals greater than 12 sec to permit measurement of the longer latency skin conductance response (SCR). In every paradigm medicated but not unmedicated schizophrenics had smaller N120 amplitudes and fewer SCRs than controls. In addition, medicated schizophrenics showed reduced P200 amplitude and latency, longer P320 latency, and reduced skin conductance levels in certain paradigms. These effects cannot easily be attributed to different mental states of medicated and unmedicated patients, since their Brief Psychiatric Rating Scale scores were almost the same. It is more probable that antipsychotic and antiparkinsonian drugs reduced electrodermal activity through anticholinergic mechanisms and that the antipsychotic drugs attenuated N120 through other biological mechanisms.

Adult↗
PubMed1991

Auditory stimulus processing at different stimulus intensities as reflected by auditory evoked potentials.

The influence of stimulus intensity on the components of auditory evoked potentials was investigated at different levels of attention and task relevance in six healthy adult subjects. A negative component with a latency of 130 msec (N130) was produced by stimuli applied as targets or nontargets in a random sequence. The N130 amplitude had an inverse U-shaped relationship to stimulus intensity, with its maximum value at a stimulus intensity of 70 dB SL. The P300 latency showed a U-shaped relationship to stimulus intensity and obtained its minimum value at 70 dB. Thus, evoked-potential equivalents of cognitive auditory stimulus processing could be shown to be loudness driven and to have highest amplitudes or shortest latencies at a stimulus loudness of 70 dB SL.

Adult↗
PubMed1992

Startle gating deficits occur across prepulse intensities in schizophrenic patients.

The effects of prepulse stimuli of different intensities in inhibiting the startle reflex was assessed in 14 age-matched and gender-matched schizophrenic patients and 14 normal controls. The subjects were presented with startling stimuli consisting of bursts of white noise (106 dBA) with or without prepulse stimuli. Four intensities of prepulse stimuli were utilized: 75, 80, 85, and 90 dBA. Throughout the testing, the background noise was maintained at 70 dBA. The prepulse stimuli more effectively inhibited the startle reflex in the control group compared to the schizophrenic patients who showed deficient prepulse inhibition (gating) of the startle reflex. These results suggest that schizophrenics have impaired central inhibitory mechanisms over a fairly broad range of background noise to prepulse ratios. Further studies are needed to clarify exactly which ratios are optimal in eliciting prepulse inhibition (PPI) and in differentiating between schizophrenic and control groups.

Adult↗
PubMed1993

Intensity dependence of auditory evoked potentials as an indicator of central serotonergic neurotransmission: a new hypothesis.

Because of the increasing importance of the central serotonergic neurotransmission for pathogenetic concepts and its role as a target of pharmacotherapeutic interventions in psychiatry, reliable indicators of this system are needed. It is proposed that the stimulus intensity dependence of auditory evoked N1/P2-component, which is probably modulated by cortical serotonergic innervation, may be a useful and noninvasive indicator of behaviorally relevant aspects of serotonergic activity. Converging evidence from our own studies as well as from the literature suggests that a pronounced intensity dependence of auditory evoked N1/P2-component reflects low central serotonergic neurotransmission. Recent findings concerning general functional aspects of the brain serotonin system reveal that this system is well qualified for adjusting individual levels of sensory processing ("set the tone"), especially in the primary auditory cortex in which the N1/P2-component is mainly generated. Dipole source analysis represents an important methodological advance in this context because it allows the separation of N1/P2-subcomponents generated in the primary auditory cortex from those generated in secondary auditory areas.

Arousal↗
PubMed1995

The Tridimensional Personality Questionnaire and the intensity dependence of auditory evoked dipole source activity.

The relationship between the tridimensional personality questionnaire's (TPQ) dimensions "novelty seeking," "harm avoidance," and "reward dependence" and the intensity dependence of the auditory evoked N1/P2-component was investigated in healthy subjects. Using dipole source analysis, evoked activity of the primary auditory cortex (tangential dipole) could be analyzed at least in part separately from that of secondary auditory areas (radial dipole). It was found that the intensity dependence of the tangential dipole was positively correlated to the TPQ dimension "novelty seeking," but not to "harm avoidance" and "reward dependence." This is in line with findings concerning similar personality traits like "sensation seeking," "impulsivity," or "extraversion." It is therefore concluded that a strong intensity dependence may characterize subjects with an action-oriented and extroverted personality style. The results are discussed within the concept that a low central serotonergic neurotransmission is underlying both an impulsive personality type and a strong intensity dependence of the tangential dipole.

Adult↗
PubMed1980

Binaural response-specific bands in primary auditory cortex (AI) of the cat: topographical organization orthogonal to isofrequency contours.

The spatial distribution of neurons with different binaural response properties has been studied within the three dimensions of the primary auditory cortex (AI) in the cat. Using dichotic stimulation, 92% of neurons encountered could be classified into either the excitatory/excitatory (EE) or excitatory/inhibitory (EI) interaction class. In nearly all of almost 800 penetrations introduced along radial axes, all neurons encountered along a given penetration were of the same binaural response class. Neurons of different binaural interaction classes were spatially segregated within the plane of the cortex. Electrode penetrations made parallel to isofrequency contours traversed the mediolateral extent of AI through the middle layers of the cortex. A sharp segregation of units by binaural response class was observed in these penetrations, i.e. sequences of neurons that were all of the EE class alternated with sequences of EI neurons. The regions of uniform response to binaural stimulation formed radially organized topographical subunits that were elongated along the rostrocaudal dimension of AI. These binaural interaction bands intersect the lines of re-representation of the cochlear sensory epithelium ('isofrequency contours') and, thus, create subdivisions of AI that each contain a representation of the entire audible frequency domain. The implications of these results for the concept of AI as a unitary element in auditory processing are discussed.

Acoustic Stimulation↗
PubMed1981

Development of the cat peripheral auditory system: input-output functions of cochlear potentials.

Compound auditory nerve action potentials (APs) and cochlear microphonics (CMs) were recorded from the round-window of kittens aged 3-9 weeks and of adult cats. Animals were anaesthetized and pure tone stimuli were delivered via calibrated, sealed, transducer systems. AP and CM amplitude and AP latency were measured over a wide range of stimulus intensities (up to 80 dB SPL) and at 5 octave-interval stimulus frequencies (1-16 kHZ). At low stimulus intensity levels, AP amplitude had attained adult levels to low and high frequency stimuli by 6 1/2 weeks of age and to mid-frequency stimuli by 9 weeks. As stimulus intensity levels were increased, the kitten input-output functions diverged progressively from those of the adults. At these higher intensity levels, AP amplitude maturation in even the 9 week animals was incomplete. AP latencies to stimuli of all frequencies shortened between the third and fourth weeks but remained stable thereafter. CM amplitude also reached maturity by the fourth week. These findings suggest that the development of AP after the fourth week consists of an increase in the synchrony of auditory nerve fibre responses, since both the fine structure of the cochlea and the responses of single nerve fibres are known to be mature by the end of the first postnatal month.

Aging↗
PubMed1981

Increasing intensities of wide band noise increase [14C]2-deoxyglucose uptake in gerbil central auditory structures.

The [14C]2-deoxyglucose (2DG) technique has been used to map the effects of increasing intensities of wide band noise on 2DG uptake in mongolian gerbil brain auditory structures. Animals were injected with [14C]2DG and exposed to silence or continuous wide band noise at 25 dB, 45 dB, 65 dB, 85 dB or 105 dB SPL. Brains were removed, frozen-sectioned and autoradiographed on X-ray film. The ratio of the optical density of gray matter structures to the optical density of cerebellar peduncles in each animal was used to semiquantitate the results. The dorsal and ventral cochlear nuclei, superior olive/trapezoid body, inferior colliculus, and the dorsal and ventral nuclei of the lateral lemniscus all showed increases in 2DG uptake during exposure to wide band noise (WBN). As noise intensity increased from 0 to 105 dB SPL, 2DG uptake increased regularly to a maximum at 85 or 105 dB SPL. As WBN intensity increased, deeper layers of inferior colliculus were activated. The medial geniculate nucleus and auditory cortex showed a lesser increase in 2DG uptake during noise exposure. Non-auditory structures, including the cerebellar cortex and the medullary reticular nuclei, showed no increase in 2DG uptake during noise exposure at any intensity tested.

Animals↗
PubMed1981

Plasticity of binaural interaction in the cat inferior colliculus.

Responses of single neurones in the inferior colliculus (IC) to acoustic interaural intensity difference (IID) were examined in normal, adult cats and in cats that had been reared for 3--4 months, either from birth or as adults, with unilateral ligation of the external meatus. There were significantly fewer units displaying IID sensitivity in either of the ligated groups than there were in the normal group. The loss of IID sensitivity in the ligated animals reflected a diminished inhibitory input from the non-ligated ear.

Aging↗
PubMed1986

Frequency sensitivities of auditory neurons in the cerebellum of the cat.

Threshold tuning curves were obtained from neurons in the cerebellar auditory area of the cat. The threshold of the brainstem auditory evoked response was also measured in each animal as a function of sound frequency in order to monitor the overall frequency sensitivity of the auditory periphery. Cerebellar auditory neurons responded to sound stimuli with little discrimination for the sound frequency. The values of Q10dB (a measure of the sharpness of tuning) were less than 2 for most of the neurons in this study. There was no significant difference in the sharpness of tuning for neurons in the various layers of the cerebellar auditory area. Electrophysiological mapping showed that the frequency sensitivity of single neurons did not appear to vary as a function of location within the cerebellar auditory area which includes lobules VI and VII of Larsell. Broad tuning was observed in long-latency (greater than 11 ms) neurons which responded to binaural sound stimuli as well as in short-latency (less than 6 ms) neurons which only responded to monaural sound stimuli. Within each animal, tuning curves of single cerebellar neurons were essentially superimposable onto each other and matched well with the overall frequency sensitivity of the animal as shown by brainstem auditory evoked response. Since the frequency tuning of these neurons appeared to reflect the overall frequency sensitivity of the auditory periphery, auditory neurons in the posterior vermis may receive inputs that involve convergence and integration from the entire length of the cochlea.

Animals↗
PubMed1980

Frequency shaping and multiband compression in hearing aids.

Compression and noncompression amplification were compared for a range of conditions. The noncompression conditions included flat-frequency response and "LDL frequency response," with and without peak clipping. The compression conditions included a single-band compression system and two combinations of a two-channel compression system. The LDL frequency response was obtained by finding the LDL for each subject using one-third octave bands of noise and then determining that frequency response which would amplify each one-third octave band of speech to just below the LDL for that band. A low-frequency roll off below 300 Hz was used to reduce upward spread of masking. Four hearing-impaired persons served as subjects. Four replications of the Nonsense Syllable Test were administered in quiet and in noise for each experimental condition. The highest scores were obtained, on the average, for the condition of noncompression, no peak clipping, with the LDL frequency response. There were, however, large individual differences in relative performance on different conditions, indicating the importance of individualized determination of optimum amplification characteristics.

Acoustics↗
PubMed1991

Listening preferences for voice types as a function of age.

This experiment was designed primarily to generate information about the preferences of older listeners for various classes of voices. Speech samples for that purpose were elicited from 80 speakers, who provided the desired stimuli (sentences) under frequency and intensity control. Specifically, there were eight cells in the design, each represented by 10 speakers (5 male and 5 female); all combinations of low, medium, and high speaker fundamental frequency (SFF) were combined with soft, middle and loud vocal intensity (VI) productions--except for the low-SFF/high-VI combination, which proved impossible to obtain. Listeners were four groups of 20 individuals equally divided as to sex. The two older of these groups, designated as the experimental subjects, were: older adults (60-70 years of age) and the elderly (80-90 years). The two younger groups served as controls; they included young adults (20-30 years of age) and middle-aged adults (aged 40-50 years). Listeners rated each speech sample on a 5-point preference scale varying from "like very much" to "dislike very much." The results suggest that most listeners prefer medium intensity voices. Other preference tendencies were toward low-pitched voices and (slightly) toward male speakers; but these trends were not as marked as the first. Most importantly, there were no systematic differences in voice type preferences between or among the older and younger groups--or between male and female listeners.

Adult↗
PubMed1982

Startle habituation in rats after lesions in the brachium of the inferior colliculus.

Bilateral interruption of the primary ascending auditory pathway at the level of the brachium of the inferior colliculus (BIC) did not affect short- or long-term habituation of the startle response provoked by auditory stimuli. Animals with BIC lesions and control animals exhibited comparable habituation following manipulations of stimulus intensity, inter-stimulus interval, and intensity of background noise, although animals with lesions in the BIC were more responsive than controls to auditory stimuli and to tactile stimuli. The integrity of the primary auditory pathway above the inferior colliculus is not necessary for short- or long-term habituation of the acoustic startle response.

Acoustic Stimulation↗
PubMed1991

Motor, but not sensory, cortical potentials are amplified by high-protein diet.

Animals fed a high-protein diet (50% casein) are hyperactive and more responsive to nociceptive stimuli than those fed either a normal- or low-protein diet. The mechanisms mediating dietary protein-induced behavior are unknown and may include both central and peripheral neural effects. Adult, Sprague-Dawley rats were fed 50% casein (treatment group) and 24% casein (control group) ad lib for 36-40 weeks. The animals were anesthetized with alpha-chloralose and urethane (50 mg/kg and 1.5 mg/kg, IP). EEG recordings were averaged while the anesthetized animal was conditioned using an alerting stimulus-imperative stimulus (AS-IS) paradigm. AS consisted of a 1.5 kHz, 90 dB tone cue. This was followed 2 seconds later by IS, an electrical tail stimulation (11 V, 1.4 s duration). Two negative deflections (N1 and N2) were generated by the frontal cortex during the AS-IS interstimulus interval. N1, an alerting response, was not different between the two groups. N2 amplitude and peak latency were significantly increased in the high-protein group (205% and 117% of control, respectively; p less than 0.05). N2 represents the activation of cells in the motor cortex. Brainstem auditory-evoked responses and somatosensory-evoked potentials also were recorded, but no differences were observed between the two diet groups. These data suggest that consumption of a high-protein diet results in an increase in central arousal mechanisms (measured by cortical negativity response), specifically involving increased excitability of the motor cortex, that is not associated with a disorder of information processing in the cerebral cortex (measured by brainstem auditory-evoked responses and somatosensory-evoked potentials).

Animals↗
PubMed1993

Sound levels in rooms housing laboratory animals: an uncontrolled daily variable.

High sound levels are known to have adverse effects on the behaviour and physiology of laboratory animals, yet their acoustic environment is rarely monitored. In particular, high-frequency sounds that are above the limit of human hearing, but are well within the limits of many laboratory species (i.e., ultrasounds), are usually ignored. In this study, the acoustic environment of laboratory animals was investigated in a variety of different animal facilities. Sound pressure levels (dB SPL) were monitored for periods up to 24 h over two frequency ranges: a relatively low range (0.01-12.5 kHz), and a high range (12.5-70 kHz). While background sound levels in undisturbed situations were generally low (i.e., below 50 dB SPL), marked increases in sound levels often occurred during the working day, producing characteristic daily variations in the sound profile. Peak SPLs commonly reached values of 80-95 dB in the low-frequency range and 50-75 dB in the higher range. In most cases, sound levels were low over weekends. The results suggested that human activities were a very important source of sound in most animal facilities. In a few situations (e.g., rabbits, marmosets, dogs), the animals themselves provided a significant contribution to the acoustic environment. It is clear that the acoustic environment of laboratory animals is a daily variable that is usually uncontrolled and that may have important implications for behavioural and physiological experiments and for animal welfare.

Animal Welfare↗