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PubMed2002

Selective deficit of auditory localisation in patients with visuospatial neglect.

Possible auditory deficits in neglect were examined by comparing the performance of four right brain-damaged (RBD) patients with left visuospatial neglect, versus four RBD patients without neglect, in three auditory tasks. The first task required speeded discrimination of sound elevation, by moving a central lever up or down according to the vertical position of a peripheral target sound, regardless of its side. The other two auditory tasks were non-spatial, requiring either speeded pitch discrimination (moving the central lever up for high pitch, down for low pitch) or speeded target detection. Neglect patients' performance was impaired with respect to RBD controls only when the auditory task required spatial coding of the target sound (the up/down spatial discrimination). This demonstrates a selective deficit of auditory space perception in neglect patients. This auditory spatial deficit was more pronounced for left than right sounds. Since auditory space perception was impaired in the vertical dimension, the observed deficit cannot be attributed to a systematic rightward shift in sound localisation. Instead, the results suggest increased spatial uncertainty in sound localisation by neglect patients, particularly for auditory targets on the contralesional side. These findings are related to multimodal coding of space in the parietal cortex, which was damaged in the neglect patients, but not in the RBD controls.

Adult↗
PubMed2001

Otoacoustic emissions and auditory assessment in infants at risk for early brain damage.

The importance of early hearing screening has long been recognized, as the prognosis for the hearing impaired child is improved when the diagnosis is made as early as possible, and the intervention is begun immediately. For clinical screening of hearing impairment, the recording of otoacoustic emissions was recommended. As some risk factors for early brain damage are at the same time also risk factors for dysfunction of auditory system, we presumed that infants at risk for brain damage have hearing impairment more frequently than the rest of the population of the same age. We were interested in the role of otoacoustic emission testing during the assessment of auditory function in these infants. There were 110 infants at risk for brain damage included in the study. After thorough otorhinolaryngological examination, auditory function was estimated by recording of otoacoustic emissions, tympanometry, pure tone audiometry and, when necessary, auditory brainstem responses. Otoacoustic emissions were recorded by Madsen-Electronics Celesta 503 in an acoustically treated sound room. We registered spontaneous as well as transient and distortion product otoacoustic emissions. The neurologist formed two groups with different degrees of neurological risk. The collected results of auditory function were compared with the degree of neurological risk. For the statistical analysis, the procedure chi(2) and Fischer test were used. Spontaneous otoacoustic emission was detected in 38.2% of examinees. Evoked otoacoustic emissions were registered in 87.3% of infants. The testing had to be repeated in 32.7% of infants. We observed evoked otoacoustic emissions to be present also in a child with sensorineural hearing impairment and no auditory brainstem responses. Up to 32.7% of infants at risk for brain damage were hard of hearing. Conductive hearing loss was discovered with 25.4% of infants, and eight (7.3%) had sensorineural hearing impairment. In the group of examinees with only risk factors 3.6% had sensorineural impairment and in a group with abnormal motor development, there were 18.5% with that kind of hearing loss. Fischer test confirmed a statistically significant difference between the groups. Infants at risk for brain damage have more frequently impaired auditory function than their peers. For this reason, it is especially important to focus attention on the hearing condition when dealing with this population. Recording of evoked otoacoustic emissions is very helpful in pediatric audiometry, but any interpretation of the results should consider the possibility of auditory neuropathy.

Acoustic Impedance Tests↗
PubMed2000

Auditory cues support place navigation in rats when associated with a visual cue.

Rats, like other crepuscular animals, have excellent auditory capacities and they discriminate well between different sounds [Heffner HE, Heffner RS, Hearing in two cricetid rodents: wood rats (Neotoma floridana) and grasshopper mouse (Onychomys leucogaster). J Comp Psychol 1985;99(3):275-88]. However, most experimental literature concerning spatial orientation almost exclusively emphasizes the use of visual landmarks [Cressant A, Muller RU, Poucet B. Failure of centrally placed objects to control the firing fields of hippocampal place cells. J Neurosci 1997;17(7):2531-42; and Goodridge JP, Taube JS. Preferential use of the landmark navigational system by head direction cells in rats. Behav Neurosci 1995;109(1):49-61]. To address the important issue of whether rats are able to achieve a place navigation task relative to auditory beacons, we designed a place learning task in the water maze. We controlled cue availability by conducting the experiment in total darkness. Three auditory cues did not allow place navigation whereas three visual cues in the same positions did support place navigation. One auditory beacon directly associated with the goal location did not support taxon navigation (a beacon strategy allowing the animal to find the goal just by swimming toward the cue). Replacing the auditory beacons by one single visual beacon did support taxon navigation. A multimodal configuration of two auditory cues and one visual cue allowed correct place navigation. The deletion of the two auditory or of the one visual cue did disrupt the spatial performance. Thus rats can combine information from different sensory modalities to achieve a place navigation task. In particular, auditory cues support place navigation when associated with a visual one.

Animals↗
PubMed2003

The morphometry of auditory cortex in the congenitally deaf measured using MRI.

The study of congenitally deaf individuals provides a unique opportunity to understand the organization and potential for reorganization of human auditory cortex. We used magnetic resonance imaging (MRI) to examine the structural organization of two auditory cortical regions, Heschl's gyrus (HG) and the planum temporale (PT), in deaf and hearing subjects. The results show preservation of cortical volume in HG and PT of deaf subjects deprived of auditory input since birth. Measurements of grey and white matter, as well as the location and extent of these regions in the deaf showed complete overlap both with matched controls and with previous samples of hearing subjects. The results of the manual volume measures were supported by findings from voxel-based morphometry analyses that showed increased grey-matter density in the left motor hand area of the deaf, but no differences between the groups in any auditory cortical region. This increased cortical density in motor cortex may be related to more active use of the dominant hand in signed languages. Most importantly, expected interhemispheric asymmetries in HG and PT thought to be related to auditory language processing were preserved in these deaf subjects. These findings suggest a strong genetic component in the development and maintenance of auditory cortical asymmetries that does not depend on auditory language experience. Preservation of cortical volume in the deaf suggests plasticity in the input and output of auditory cortex that could include language-specific or more general-purpose information from other sensory modalities.

Adult↗
PubMed1994

Yohimbine impairs P50 auditory sensory gating in normal subjects.

The evoked response to repeated auditory stimuli generally decreases in amplitude, a phenomenon that demonstrates the activity of sensory gating mechanisms in the central nervous system (CNS). Gating of the P50 wave of the auditory evoked response shows such behavior in normals, but not in schizophrenic or manic subjects. In mania, diminished gating of the auditory evoked response is correlated with elevated levels of noradrenergic metabolites. In animals, yohimbine, a presynaptic alpha-2 antagonist, increases noradrenergic neuronal transmission in the CNS and diminished gating of the auditory evoked response. The aim of this experiment was to test whether yohimbine causes diminished auditory sensory gating in normal human controls. Seven normal subjects with normal P50 auditory gating were treated either with 0.4 mg/kg of oral yohimbine on one day or placebo on a different day. Each subject acted as his own control. Yohimbine, but not placebo, caused a significant but transient decrease in P50 auditory gating in these subjects. Thus, increasing CNS noradrenergic neuronal transmission in normal controls can cause a transient impairment in auditory sensory gating.

Acoustic Stimulation↗
PubMed1990

Simple triangular approximations of auditory filter shapes.

At present, the most popular auditory filter shape model is one with a rounded peak and exponentially decaying filter skirts (Patterson & Moore, 1986). Unfortunately, the complex nature of this "roex" filter model may, in some instances, have hindered the application of the auditory filter shape in clinical measurements of frequency selectivity. Moreover, some of the assumptions of the roex filter model may be violated at high sound-pressure levels (SPLs) and this limitation has also been a factor when considering the roex auditory filter shape in the clinic. Our purpose is to introduce a simplified method that is adequate for obtaining clinically useful estimates of triangular-shaped auditory filters. Although the triangular-shaped filter model faces the same problems as the roex model at high SPLs, the calculations and assumptions underlying the former are far less complicated. The triangular filter model also retains many of the qualitative properties and advantages afforded by roex-fitted auditory filter shapes. In this report, we review the basic concepts underlying auditory filter shape estimates and describe our methods for measuring and fitting the triangular-shaped filter model. We then present normative triangular filter shapes and compare these estimates with auditory filter shapes fitted by other means. Finally, we present selected examples of triangular filter shapes fitted to the masked thresholds of hearing-impaired patients. For the most part, the triangular-shaped filter model offers the clinician a satisfactory compromise for obtaining estimates of auditory filter shape and frequency selectivity at moderately intense and high SPLs.

Adult↗
PubMed2003

Potentiation of amygdaloid and hippocampal auditory-evoked potentials in a discriminatory fear-conditioning task in mice as a function of tone pattern and context.

According to the local memory storage hypothesis, information about the tone-shock association in an auditory fear-conditioning paradigm is stored in synapses within the lateral amygdala. Thus, fear-conditioning-induced potentiation of auditory-evoked potentials in response to a conditioned stimulus (CS+, a series of short lasting tones; patterned tone) has been interpreted as an in vivo correlate of amygdaloid synaptic plasticity. Here, we re-examine the specificity of potentiation of auditory-evoked potentials in terms of (i) local confinement to the lateral amygdala, (ii) parameters of CS+ and (iii) influence of context, using a discriminatory fear-conditioning paradigm. Adult male C57BL/6J mice were implanted with recording electrodes aimed at the lateral amygdala, the CA1 region of the hippocampus and the neck muscles for simultaneous recordings of auditory-evoked potentials and startle responses. In a neutral context, auditory-evoked potentials within lateral amygdala and CA1 as well as startle and freezing responses to the CS+ were significantly potentiated following conditioning, as compared with pre-conditioning values and responses to a neutral stimulus (CSn; tone of different frequency). Potentiation was only evident if CS+ was presented as a uniform series but not if presented mixed with CSn. Accordingly, mice failed to show intensified freezing to a patterned tone if a single lasting tone of the same frequency served as CS+. Both CA1 and lateral amygdala auditory-evoked potentials were potentiated in response to CSn if presented in the conditioning context. These findings demonstrate that (i) potentiation of auditory-evoked potentials is not restricted to the lateral amygdala, (ii) both tone frequency and pattern of tone presentation are essential for proper CS+ recognition and (iii) contextual memory leads to a general potentiation of auditory-evoked potentials.

Acoustic Stimulation↗
PubMed1998

[Visualization of central auditory processes with functional magnetic resonance tomography].

BACKGROUND: Central auditory processes can be visualized using functional MRI in a non-invasive manner and at high spatial resolution. Acoustic stimulation leads to an increase of blood flow of activated areas in the plane of the superior temporal gyrus. Radiologically, this may be visualized based on the long T2-relaxation time of oxyhemoglobin. PATIENTS: Ten normal-hearing subjects with ages between 28 and 38 years took part in the investigations. They received binaural, monaural right, and monaural left stimulation with pulsed sine tones of 1000 Hz at a pulse rate of 6 Hz and a sound pressure level of 100 dB SPL. Tonotopic organization of the auditory cortex was visualized using stimulation by pulsed sine tones of 500 Hz and 4000 Hz. RESULTS: Following monaural acoustic stimulation, increased activity of the contralateral auditory cortex could be demonstrated in 9 subjects. In one subject, bilateral activity was noted. Concerning the tonotopic organization of the auditory cortex, we could show that the higher frequencies were localized more medially and anteriorly; the lower frequencies were localized more laterally and posteriorly in the superior temporal gyrus. However, considerable overlap was noted. CONCLUSIONS: The overlap of the different frequencies could explain the controversial discussion of the tonotopic organization of the auditory cortex. The results of the monaural acoustic stimulation show clearly the predominant signal increase of contralateral areas in the primary auditory cortex. These results confirm the opinion of the current textbooks that the fiber of the auditory pathways mostly cross. Further investigations using functional MRI are necessary for better understanding of physiological and pathophysiological central-auditory processes.

Acoustic Stimulation↗
PubMed2003

Spatial variations of visual-auditory fusion areas.

The tolerance to spatial disparity between two synchronous visual and auditory components of a bimodal stimulus has been investigated in order to assess their respective contributions to perceptual fusion. The visual and auditory systems each have specific information-processing mechanisms, and provide different cues for scene perception, with the respective dominance of space for vision and of time for hearing. A broadband noise burst and a spot of light, 500 ms in duration, have been simultaneously presented to participants who had to judge whether these cues referred to a single spatial event. We examined the influence of (i) the range and the direction of spatial disparity between the visual and auditory components of a stimulation and (ii) the eccentricity of the bimodal stimulus in the observer's perceptual field. Size and shape properties of visual-auditory fusion areas have been determined in two dimensions. The greater the eccentricity within the perceptual field, the greater the dimension of these areas; however, this increase in size also depends on whether the direction of the disparity is vertical or horizontal. Furthermore, the relative location of visual and auditory signals significantly modifies the perception of unity in the vertical plane. The shape of the fusion areas, their variation in the field, and the perceptual result associated with the relative location of the visual and auditory components of the stimulus, concur towards a strong contribution of audition to visual-auditory fusion. The spatial ambiguity of the localisation capabilities of the auditory system may play a more essential role than accurate visual resolution in determining fusion.

Adult↗
PubMed1999

Spatial and temporal patterns of evoked neural activity from auditory nuclei in chick brainstem detected by optical recording.

In order to detect the spatial patterning of the auditory projection of the embryonic chick brainstem, anatomical methods such as orthograde transport of horseradish peroxidase have been used. However, these methods do not provide the continuous information required about the absolute value and time-course of varying neural excitement. Furthermore, the use of conventional electrophysiological methods makes it difficult or impossible to detect the transmembrane voltage change because of the small size and fragility of the cells of the young chick brainstem. We thus believe that optical measurement of membrane potential might be beneficial in circumstances where electrodes are difficult to use for reasons of cell size, complexity, or membrane topology. In the present work, we therefore examined the feasibility of an optical method for delineating the synaptic transmission of afferent input in the auditory nuclei in the chick brainstem. We used embryonic chick brainstem slice preparations featuring an intact eighth nerve, and loaded depolarizing square current pulses from tungsten microelectrodes into the auditory nerve for stimulation of these preparations. In this approach, we used a multiple-site optical recording system comprising a 16 x 16-element photodiode array and a voltage sensitive dye (NK-2761). Neural excitation evoked by stimulation to the left auditory nerve was propagated to the dorsal side of the brainstem. This area in which the optical signal was detected is located on the auditory nuclei. Since the physiological spatial patterning of the auditory nerve projection could be roughly estimated by the optical technique, the technique is considered useful for examining the electrical activity generated from auditory nuclei in the brainstem. This is the first report of spatial patterning of auditory neurons in the embryonic chick brainstem generated through optical recording.

Animals↗
PubMed2001

The influence of moving auditory stimuli on standing balance in healthy young adults and the elderly.

The maintenance of postural balance depends on effective and efficient feedback from various sensory inputs. The importance of auditory inputs in this respect is not, as yet, fully understood. The purpose of this study was to analyse how the moving auditory stimuli could affect the standing balance in healthy adults of different ages. The participants of the study were 12 healthy volunteers, who were divided into two age categories: the young group (mean = 21.9 years) and the elderly group (mean = 68.9 years). The instrument used for evaluation of standing balance was a force plate for measuring body sway parameters. The toe pressure was measured using the F-scan Tactile Sensor System. The moving auditory stimulus produced a white-noise sound and binaural cue using the Beachtron Affordable 3D Audio system. The moving auditory stimulus conditions were employed by having the sound come from the right to left or vice versa at the height of the participant's ears. Participants were asked to stand on the force plate in the Romberg position for 20 s with either eyes opened or eyes closed for analysing the effect of visual input. Simultaneously, all participants tried to remain in the standing position with and without auditory stimulation that the participants heard from the headphone. In addition, the variables of body sway were measured under four conditions for analysing the effect of decreased tactile sensation of toes and feet soles: standing on the normal surface (NS) or soft surface (SS) with and without auditory stimulation. The participants were asked to stand in a total of eight conditions. The results showed that the lateral body sway of the elderly group was more influenced than that of the young group by the lateral moving auditory stimulation. The analysis of toe pressure indicated that all participants used their left feet more than their right feet to maintain balance. Moreover, the elderly had the tendency to be stabilized mainly by use of their heels. The young group were mainly stabilized by the toes of their feet. The results suggest that the elderly may need a more appropriate stimulus of tactile and auditory sense as a feedback system than the young for maintaining and control of their standing postures.

Acoustic Stimulation↗
PubMed2002

Hearing restoration with auditory brainstem implant in three children with cochlear nerve aplasia.

OBJECTIVE: To verify the possibility of auditory habilitation in children with aplasia and hypoplasia of the cochlear nerve by direct electrical stimulation of the cochlear nuclei with an auditory brainstem implant. STUDY DESIGN: Retrospective case review. SETTING: Study conducted at the Ear, Nose, and Throat Department of the University of Verona, Italy. PATIENTS: Three children, aged 4, 3, and 2 years, respectively, with severe bilateral cochlear malformations and cochlear nerve aplasia have received an auditory brainstem implant at this institution in the past 2 years. INTERVENTION: The classic retrosigmoid approach was used. Correct positioning of the electrodes was evaluated using electric auditory brainstem responses and neural response telemetry. Before the patients were discharged, high-resolution computed tomography with a bone algorithm reconstruction technique was performed to evaluate electrode placement. The auditory brainstem implant was activated 30 to 60 days after implantation. RESULTS: No postoperative complications were observed. To date, 21, 18, and 8 electrodes, respectively, have been activated in the three children. The first patient, 12 months after activation, had achieved good environmental sound awareness, good speech detection, and some speech recognition. The second child, 8 months after activation, had achieved good environmental sound awareness and moderate speech detection. The third patient, 1 month after activation, had obtained good environmental sound awareness. CONCLUSION: This study indicates that auditory brainstem implantation is technically feasible in children with cochlear nerve aplasia. The early results suggest the possibility of achieving auditory habilitation with auditory brainstem implantation in this population.

Algorithms↗
PubMed2005

The jaundiced gunn rat model of auditory neuropathy/dyssynchrony.

OBJECTIVE: High levels of bilirubin are neurotoxic and may result in deafness or auditory neuropathy/auditory dyssynchrony (AN/AD). The jaundiced (jj) Gunn rat animal model of kernicterus has electrophysiologic and neuroanatomic abnormalities of brainstem auditory nuclei with normal cochlear microphonic recordings. We examined morphologic changes in the cochlea, spiral ganglion, and auditory nerve and relate these findings to current understanding of AN/AD. METHODS: At 15 days of age, jj and nonjaundiced (Nj) littermates were injected with sulfadimethoxine (sulfa) and killed 3 days later by transcardial perfusion. Sections were cut through decalcified temporal bones, cochlear nerves, and auditory brainstem and processed for light and electron microscopy and immunohistochemical localization of calbindin-D and parvalbumin. RESULTS: Spiral ganglion neurons were severely degenerated with a paucity of myelinated axons in jj animals. Electron microscopy of the intramodilar auditory nerve revealed a lack of large caliber axons in jj-sulfa versus Nj-sulfa controls. Large diameter degenerating axons were characterized by an electron-dense atrophied axis cylinder resembling an axonopathy. CONCLUSIONS: Our findings of abnormal spiral ganglion cells and selective loss of large, myelinated auditory nerve fibers with no abnormalities in cochlear hair cells, support the sulfa-treated jj Gunn rat as a model for bilirubin induced AN/AD. The paucity of large caliber neurons undermines temporal coding of auditory information and neural synchrony and demonstrates that in addition to brainstem auditory nuclei, spiral ganglion neurons are selectively vulnerable to bilirubin toxicity.

Animals↗
PubMed1983

Cells responsive to free-field auditory stimuli in guinea-pig superior colliculus: distribution and response properties.

We have investigated the responses of superior colliculus neurones in the anaesthetized guinea-pig to free-field auditory stimulation. The auditory cells were located throughout the deeper laminae and also in the lower part of the stratum opticum. Auditory cells were not found in the rostral pole of the superior colliculus. The auditory responses consisted of a few spikes at stimulus onset with a latency from stimulus arrival at the ear of 7-27 ms. Frequency response areas were measured for forty-five neurones; many of these areas were broad or multipeaked although some were well defined and 'V' shaped. White noise was a more effective stimulus than tones. The majority of cells in our sample responded best to sounds from a restricted horizontal location. Two major response types were found: (1) neurones responding to the same localized area of space despite changes in sound level and (2) neurones responding only to a localized area of space near threshold, but to an extensive area for louder sounds. As the site of the recording electrode was moved from the rostral to the caudal part of the superior colliculus, the location of the auditory receptive fields shifted from the anterior to the posterior field of the animal, thus indicating the presence of a map of auditory space. The visual projection to the guinea-pig superior colliculus was determined and found to be similar to that in other vertebrates. Comparison of visual and auditory space maps in the guinea-pig superior colliculus reveals that receptive fields are coincident over a wide range, but severe discrepancies were evident between the visual and auditory receptive field positions represented at single locations in rostral and caudal colliculus.

Acoustic Stimulation↗
PubMed2000

The use of visible speech cues for improving auditory detection of spoken sentences.

Classic accounts of the benefits of speechreading to speech recognition treat auditory and visual channels as independent sources of information that are integrated fairly early in the speech perception process. The primary question addressed in this study was whether visible movements of the speech articulators could be used to improve the detection of speech in noise, thus demonstrating an influence of speechreading on the ability to detect, rather than recognize, speech. In the first experiment, ten normal-hearing subjects detected the presence of three known spoken sentences in noise under three conditions: auditory-only (A), auditory plus speechreading with a visually matched sentence (AV(M)) and auditory plus speechreading with a visually unmatched sentence (AV(UM). When the speechread sentence matched the target sentence, average detection thresholds improved by about 1.6 dB relative to the auditory condition. However, the amount of threshold reduction varied significantly for the three target sentences (from 0.8 to 2.2 dB). There was no difference in detection thresholds between the AV(UM) condition and the A condition. In a second experiment, the effects of visually matched orthographic stimuli on detection thresholds was examined for the same three target sentences in six subjects who participated in the earlier experiment. When the orthographic stimuli were presented just prior to each trial, average detection thresholds improved by about 0.5 dB relative to the A condition. However, unlike the AV(M) condition, the detection improvement due to orthography was not dependent on the target sentence. Analyses of correlations between area of mouth opening and acoustic envelopes derived from selected spectral regions of each sentence (corresponding to the wide-band speech, and first, second, and third formant regions) suggested that AV(M) threshold reduction may be determined by the degree of auditory-visual temporal coherence, especially between the area of lip opening and the envelope derived from mid- to high-frequency acoustic energy. Taken together, the data (for these sentences at least) suggest that visual cues derived from the dynamic movements of the fact during speech production interact with time-aligned auditory cues to enhance sensitivity in auditory detection. The amount of visual influence depends in part on the degree of correlation between acoustic envelopes and visible movement of the articulators.

Adult↗
PubMed1997

Neural contributions to the perstimulus compound action potential: implications for measuring the growth of the auditory nerve spike count as a function of stimulus intensity.

The perstimulus compound action potential (PCAP), unlike the more familiar compound action potential (CAP), can be recorded in response to asynchronous as well as synchronous auditory nerve activity. When all neurons contribute equally to the PCAP, the area under the PCAP (the PCAP area) is proportional to the number of action potentials fired by auditory nerve neurons (the auditory nerve spike count). The auditory nerve spike count is one proposed code for stimulus intensity, and our goal is to use the PCAP to test this hypothesis. In this study, two independent tests were developed to measure the contributions of neurons to the PCAP as a function of their characteristic frequency (CF). The test results were verified using a model of the auditory periphery designed to calculate the auditory nerve spike count as a function of pure tone intensity and frequency. In nearly all experiments, neurons having CFs that span contiguous three or four octave bands contribute equally to the PCAP. For pure tones that stimulate only those neurons contributing equally to the PCAP, the PCAP area grows over intensity ranges frequently exceeding 80 dB, and in one case equaling 108 dB. These results demonstrate that the auditory nerve spike count, at least for pure tones, is capable of encoding changes in stimulus intensity over the entire dynamic range of the auditory system.

Animals↗
PubMed1987

Auditory pathways to the frontal cortex of the mustache bat, Pteronotus parnellii.

In primates, certain areas of the frontal cortex play a role in guiding movements toward visual or auditory objects in space. The projections from auditory centers to the frontal cortex of the bat Pteronotus parnellii were examined because echolocating bats utilize auditory cues to guide their movements in space. An area in the frontal cortex receives a direct projection from a division of the auditory thalamus, the suprageniculate nucleus, which in turn receives input from the anterolateral peri-olivary nucleus, an auditory center in the medulla. This pathway to the frontal cortex bypasses the main auditory centers in the midbrain and cortex and could involve as few as four neurons between the cochlea and the frontal cortex. The auditory cortex is also a major source of input to the frontal cortex. This area of the frontal cortex may link the auditory and motor systems by its projections to the superior colliculus.

Animals↗
PubMed1998

Auditory hallucinations in Parkinson's disease.

Whereas visual hallucinations are often found among patients with Parkinson's disease, the occurrence of auditory hallucinations has never been systematically documented. The occurrence, past and present, of auditory hallucinations has been studied in 121 consecutive patients with Parkinson's disease attending a movement disorders clinic. The cognitive state was evaluated using the short mental test (SMT). Hallucinations were reported for 45 patients (37%); 35 (29%) had only visual hallucinations and 10 (8%) both visual and auditory hallucinations. No patient reported auditory hallucinations unaccompanied by visual hallucinations. The auditory hallucinations occurred repeatedly, consisting of human voices. They were non-imperative (n=9), non-paranoid (n=9), and often incomprehensible (n=5). They were not obviously influenced by the patients' age, duration of disease, or treatment with levodopa. Cognitive impairment was more common among hallucinating patients (64%, 50%, and 25% among patients with visual hallucinations, auditory hallucinations, and nonhallucinating parkinsonian patients respectively). Depression necessitating antidepressants was present in five of 10 and other psychotic features in six patients with auditory hallucinations. It is concluded that auditory hallucinations occur in Parkinson's disease, particularly in patients who also have visual hallucinations and are cognitively impaired.

Aged↗