Auditory brainstem responses in 10 inbred strains of mice

The auditory brainstem response (ABR) is an evoked potential response of auditory activity in the auditory nerve and subsequent fiber tracts and nuclei within the auditory brainstem pathways. The threshold, amplitude, and latency analysis of the ABR provides information on the peripheral hearing status and the integrity of brainstem pathways. In this study, we compared the threshold, amplitude, and latency of ABRs recorded from 149 mice of 10 commonly used inbred strains (BALB/cJ, C3HeB/FeJ, C3H/HeJ, CAST/EiJ, CBA/CaJ, CBA/J, FVB/NJ, MRL/MpJ, NZB/BlNJ, and SJL/J) using clicks of different intensities. The ABR thresholds of these strains ranged from 32 to 43 dB SPL. The amplitude of both waves I and IV of ABRs, which increased monotonically with click intensity in most strains, differed significantly among different strains at each intensity tested. Moreover, the amplitude of both waves was inversely correlated with the body weight of each strain at most intensities tested. In general, the amplitude of wave IV was smaller than that of wave I resulting in the IV/I amplitude ratio of <1.0 in all strains. The peak latency of both waves I and IV decreased significantly with click intensity in each strain. However, this intensity-dependent decrease was greater for wave IV than for wave I such that the wave I-IV inter-peak latency also decreased significantly with increasing intensity. I-IV inter-peak latencies for MRL/MpJ, C3HeB/FeJ, NZB/BlNJ, and C3H/HeJ strains are longer than FVB/NJ, SJL/J, or CAST/EiJ. This work is the first step to study the genetic basis underlying strain-related differences in auditory pathway.     

Effects of pentylenetetrazole and 4-aminopyridine on the auditory brainstem response (ABR) and on the hearing sensitivity in the guinea pig in vivo

For exploring a possible connection between the reduced hearing sensitivity and certain abnormalities in the auditory brainstem responses (ABRs) in generalized epilepsy, the effects of two convulsing agents, namely pentylenetetrazole (PTZ) and of 4-aminopyridine (4-AP), on: (1). the cortical activity (EEG), (2). the hearing threshold and (3). the amplitudes and latencies of the ABR waves evoked by a stimulus of high intensity (100 dB) were investigated in guinea pigs. All animals injected (i.p.) with 100mg/kg PTZ or with 2mg/kg 4-AP developed generalized seizures, followed by characteristic EEG patterns for the post-ictal period, that were accompanied by a marked reduction of the hearing sensitivity (as indicated by the elevated threshold of the ABR), as well as by retro-cochlear changes (as judged by the changes in the later ABR waves in response to 100 dB). For instance, both convulsing agents decreased the amplitude and increased the latency of P4, that is the wave component of the ABRs generated in the lateral superior olivary nucleus and while PTZ increased the latency of P3, the wave component of the ABRs generated in the medial superior olivary nucleus, 4-AP dramatically increased its amplitude. Comparison of recordings taken at specific times for the duration of the post-ictal period (i.e. within about 1h for PTZ and 2h for 4-AP) reveals that the extent of the changes on the EEG matches with the increase in the auditory threshold and with the extent of the changes on the later waves of the ABR elicited by 100 dB. These data indicate that changes in the activity of the lateral and the medial nuclei of the superior olivary complex (SOC) accompany the hearing loss and the post-ictal epileptic cortical activity.     

Anatomical bases of binaural interaction in auditory brain-stem responses from guinea pig

There is a non-linear interaction of binaural stimulation on auditory brain-stem potentials in both human and animals. The interaction takes the form of the binaurally evoked ABR being of smaller amplitude than the sum of the monaurally evoked ABRs. In the guinea pig this interaction occurs at the time of components P4, N4 and P5. In order to investigate the generator sites of binaural interaction in the ABR, various lesions were made in the brain-stem auditory system in 29 guinea pigs. The effects of those lesions on binaural interaction were as follows: (1) unilateral lesion of lateral lemniscus or bilateral lesions of the inferior colliculi had no significant effect on binaural interaction; (2) transection of the lateral lemnisci bilaterally was associated with a loss of the component of binaural interaction associated in time with N4; (3) a lesion just lateral to the lateral superior olivary complex resulted in an attenuation of the component of binaural interaction associated in time with P4; (4) complete section of the decussating fibers of the trapezoid body or a complete unilateral lesion of the superior olivary complex led to a loss of all components of binaural interaction. These results suggest that binaural interaction in the guinea pig ABR requires the integrity of several distinct portions of the brain-stem auditory pathway, i.e., both lateral lemnisci are required for the interaction occurring at the time of N4; the brain-stem just lateral to the lateral superior olive participates in the interaction at the time of P4. The trapezoid body and superior olivary nucleus are required for binaural interaction at P4, N4 and P5.     

Age‐related neurochemical changes in the rhesus macaque superior olivary complex

Positive immunoreactivity to the calcium‐binding protein parvalbumin (PV) and nitric oxide synthase NADPH‐diaphorase (NADPHd) is well documented within neurons of the central auditory system of both rodents and primates. These proteins are thought to play roles in the regulation of auditory processing. Studies examining the age‐related changes in expression of these proteins have been conducted primarily in rodents but are sparse in primate models. In the brainstem, the superior olivary complex (SOC) is crucial for the computation of sound source localization in azimuth, and one hallmark of age‐related hearing deficits is a reduced ability to localize sounds. To investigate how these histochemical markers change as a function of age and hearing loss, we studied eight rhesus macaques ranging in age from 12 to 35 years. Auditory brainstem responses (ABRs) were obtained in anesthetized animals for click and tone stimuli. The brainstems of these same animals were then stained for PV and NADPHd reactivity. Reactive neurons in the three nuclei of the SOC were counted, and the densities of each cell type were calculated. We found that PV and NADPHd expression increased with both age and ABR thresholds in the medial superior olive but not in either the medial nucleus of the trapezoid body or the lateral superior olive. Together these results suggest that the changes in protein expression employed by the SOC may compensate for the loss of efficacy of auditory sensitivity in the aged primate. J. Comp. Neurol. 522:573–591, 2014. © 2013 Wiley Periodicals, Inc.     

GABAergic neurons and axon terminals in the brainstem auditory nuclei of the gerbil

The anatomical localization of glutamic acid decarboxylase (GAD), the synthesizing enzyme for GABA, was analyzed in the brainstem auditory nuclei of the adult gerbil. GAD-positive terminals and somata were present in the cochlear nucleus, superior olivary complex, lateral lemniscus, and inferior colliculus in varying concentrations and patterns. One of the highest densities of GAD-positive terminals is found in the superficial layers of the dorsal cochlear nucleus (DCN), whereas the ventral cochlear nucleus (VCN) has somewhat fewer terminals that are arranged in pericellular plexuses. GAD-positive neurons occur mainly in the superficial and fusiform layers of the DCN and are scattered throughout the VCN. Within the superior olivary complex, the highest concentration of immunoreactive terminals and neurons occurs in the ventral and lateral nuclei of the trapezoid body. In contrast, the medial nucleus of the trapezoid body and the medial superior olive contain fewer GAD-positive puncta and probably no immunoreactive somata. The lateral superior olive and superior periolivary nucleus contain a few immunoreactive puncta but a large number of immunoreactive somata. In the midbrain, the nuclei of the lateral lemniscus contain a moderate number of GAD-positive puncta and a large number of different types of GAD-positive neurons. The inferior colliculus also contains a heterogeneous population of labeled somata, most of which are multipolar neurons. In addition, a high concentration of immunoreactive puncta occurs in this region. These data demonstrate a diverse distribution of GAD-positive neurons and puncta throughout the brainstem auditory nuclei and suggest that GABA might be an important neurotransmitter in the processing of auditory information.     

The temporal relationship between speech auditory brainstem responses and the acoustic pattern of the phoneme /ba/ in normal-hearing adults.

OBJECTIVE: To investigate the temporal relationship between speech auditory brainstem responses and acoustic pattern of the phoneme /ba/. METHODS: Speech elicited auditory brainstem responses (Speech ABR) to /ba/ were recorded in 23 normal-hearing subjects. Effect of stimulus intensity was assessed on Speech ABR components latencies in 11 subjects. The effect of different transducers on electromagnetic leakage was also measured. RESULTS: Speech ABR showed a reproducible onset response (OR) 6ms after stimulus onset. The frequency following response (FFR) waveform mimicked the 500Hz low pass filtered temporal waveform of phoneme /ba/ with a latency shift of 14.6ms. In addition, the OR and FFR latencies decreased with increasing stimulus intensity, with a greater rate for FFR (-1.4ms/10dB) than for OR (-0.6ms/10dB). CONCLUSIONS: A close relationship was found between the pattern of the acoustic stimulus and the FFR temporal structure. Furthermore, differences in latency behaviour suggest different generation mechanisms for FFR and OR. SIGNIFICANCE: The results provided further insight into the temporal encoding of basic speech stimulus at the brainstem level in humans.     

Postnatal development of auditory function in the chicken revealed by auditory brain-stem responses (ABRs)

Auditory evoked brain-stem responses (ABRs) were recorded from the surfaces of the brain of lightly anesthetized newborn (1-7 days old) and adult (7-9 weeks old) chickens as a measure of the development of auditory processing. One-day-old and older chickens showed a series of waves within 5 msec after the stimulus onset. This precocity of the ABR in chickens contrasts with the first appearance of the ABR in cats at 4 days of age. The ABR onset latency was shorter in adult chickens than in newborns. This indicates that developmental modifications of mechanical transmission in the external and middle ear or cytodifferentiation of the sensory hair cells of the basillar papilla and the neurons of the acoustic nerve continue postnatally. Within the complex wave form of the response, most of the inter-wave latencies decreased with maturation, indicating that development of the central auditory pathway also continues postnatally. One inter-wave latency (N1 to P3-4) was significantly shorter (P less than 0.05) in adults than in newborns for intense click stimuli, and even among newborns, this inter-wave latency was significantly shorter in 6- and 7-day-old specimens than in 1-3-day-old specimens. It seems likely that changes in the N1 to P3-4 inter-wave latency reflect changes in evoked activity of second order auditory neurons that are located in the nucleus angularis and nucleus magnocellularis, and that intensive developmental changes occur in these neurons during the first postnatal week. The ABR recorded in chickens is a reliable measure of functional activity in the auditory system which is reproducible between individuals and capable of demonstrating developmental changes in specific segments of the wave form.     

Far-field recorded frequency-following responses: evidence for the locus of brainstem sources.

Two experiments were performed to determine the brainstem origins of the scalp recorded auditory frequency-following response (FFR). The first was a study of FFR onset latency in which responses observed by direct recording from depth electrodes in brainstem auditory nuclei were compared with those obtained from the scalp. The mean onset latency of scalp recorded FFR (5.8 msec) closely approximated the 5.4 msec mean latency of response recorded from within the inferior colliculus (IC). In a second experiment, cooling of the IC greatly reduced or eliminated FFR both within this nucleus and at the scalp. FFR at the medial superior olive was unaffected during cooling. It was concluded that at moderate intensities of stimulation the primary source of scalp recorded FFR is the IC.     

Depth evoked potential and single unit correlates of vertex midlatency auditory evoked responses

The rostral brainstem and thalamus of awake cats were studied for depth correlates of a surface-recorded midlatency auditory evoked potential, wave "A', with a latency range of 17-25 ms. In response to clicks or pure tones, midlatency potentials were recorded from the level of the cuneiform nucleus (14-15 ms latencies) forward through the medial tegmentum to the level of the intralaminar thalamic nuclei centralis lateralis (CL) and center median (CM) (17-19 ms latencies). While this medial projection system to the thalamus involved primarily CL and CM, slightly longer latency responses were also found in nucleus ventralis anterior (VA) and ventralis lateralis (VL). A ventral diencephalic response was characterized by latencies averaging 0.5-1.2 ms less than those from the dorsal thalamic regions. Both surface and depth midlatency potentials showed comparable sensitivity to rate of stimulation. At click rates above 1/s, peak amplitudes diminished, and for rates greater than 10/s, both surface and depth midlatency responses were abolished. This rate sensitivity differs from that of the auditory brainstem responses (ABRs), which are essentially unchanged at rates of 20/s. Whereas ABRs are unaffected by surgical levels of sodium pentobarbital, the surface and depth midlatency potentials are replaced by a deep negativity within minutes following administration of anesthesia. Extracellular recordings of acoustically responsive single units in CL and CM demonstrated latencies comparable to the CL and CM field potential latencies. Both the units and field potentials were similarly rate sensitive. Each auditory unit showed a best frequency response, but none demonstrated somatosensory convergence. Bilateral aspiration of the inferior colliculus did not abolish the midlatency depth or surface responses. Rather, recordings in CL and CM suggested response enhancement over a two week postoperative period. Taken together these data suggest that the midlatency vertex potential, wave "A', reflects a generator system which projects from cuneiform nucleus, through the medial tegmentum to the medial thalamus, particularly to CL and CM. The functional significance of this medial auditory projection system remains to be determined. It could mediate physiological correlates of "state', modulate sensory input or motor output, or it could provide an integrative mechanism for the focusing of auditory attention.     

Fibroblast growth factor-2-like immunoreactivity in auditory brainstem nuclei of the developing and adult rat: Correlation with onset and loss of hearing

Fibroblast growth factor-2 (FGF-2; basic FGF) is widely distributed in the developing and adult brain and has numerous effects on cultured and lesioned neural cells. The physiological role of FGF-2 in the unlesioned nervous system, however, is still not understood. We have studied the distribution of FGF-2 in the developing, adult, and functionally impaired central auditory system of the rat using specific antibodies and peroxidase-antiperoxidase immunocytochemistry. FGF-2-like immunoreactivity (FGF-2-IR) occurred in neuronal cell bodies and/or nerve fibers but was very rarely observed in glial cells. Several auditory brainstem nuclei, including the superior paraolivary nucleus, the medial superior olive, the lateral and ventral trapezoid nuclei, and the central nucleus, as well as the external cortex of the inferior colliculus, were entirely devoid of FGF-2-IR. In the dorsal cochlear nucleus, the lateral superior olive, and the nuclei of the lateral lemniscus, FGF-2-IR was not detectable in nerve cell bodies prior to adult age. Neurons in the medial geniculate body exhibited FGF-2-IR only transiently, from postnatal day (P) 5 until P16. Neurons in the medial nucleus of the trapezoid body were immunoreactive from P8 onwards. FGF-2-IR in anteroventral and posteroventral cochlear neurons disappeared at P14, i. e., at the onset of hearing, but immunoreactivity returned after P21. A transient expression of FGF-2 around the time when hearing function commences was observed in the dorsal cortex of the inferior colliculus. Thus, regulation of neuronal FGF-2-IR in several, but not all, auditory, nuclei is related to the onset of hearing, in that IR disappears at that time or transiently appears. This suggests a causal link between the onset of hearing and FGF-2 expression. In support of this notion, ototoxic treatment with gentamycin abolished FGF-2-IR in the P16 medial geniculate body but not in other auditory brainstem centers. Thus, FGF-2 may be considered a regulator or indicator of the acquisition of functional activity and responsiveness to sensory stimuli in several areas of the auditory system. © 1995 Wiley-Liss, Inc.     

Development of ventral cochlear nucleus projections to the superior olivary complex in gerbil

The postnatal development of the projection from the ventral cochlear nucleus to the principal nuclei in the superior olivary complex in gerbil (Meriones unguiculatus) was studied in an age-graded series of pups ranging from 0 to 18 days old. Small crystals of 1, 1′-dioctadecyl3, 3, 3′, 3′-tetramethylindocarbocyanine perchlorate (DiI) were inserted into the ventral cochlear nucleus of aldehyde-fixed brains, and the labeled projections were examined with epifluorescence microscopy. Selected sections were photooxidized in a solution of diaminobenzidine and subsequently processed for electron microscopy to examine the development of labeled synapses in the target nuclei. Horseradish peroxidase was injected into the ventral cochlear nucleus of adult gerbils to assess the form and persistence of projections observed in the neonatal animals. In addition, electrophysiological responses to acoustic stimuli of single units in the adult auditory brainstem were analyzed to confirm the functionality of the novel projection from the ventral cochlear nucleus to the contralateral lateral superior olive. By the day of birth (PO), developing axons from the ventral cochlear nucleus have already established highly ordered pathways to the three primary nuclei of the superior olivary complex: the ipsilateral lateral superior olive, the contralateral medial nucleus of the trapezoid body, and at the lateral and medial dendrites of the ipsilateral and contralateral medial superior olive, respectively. Developing axons from the ventral cochlear nucleus that innervated the contralateral medial nucleus of the trapezoid body lacked the terminal morphology characteristic of the calyx of Held, but began to adopt a more characteristic form on P5. The mature calyx appeared around P14–16. Exuberant developmental projections to topographically inappropriate areas of the superior olivary complex were not observed at the postnatal ages studied. In addition to the projections of the ventral cochlear nucleus to the superior olivary complex described in other species, we observed the development and maintenance of a major direct projection from the ventral cochlear nucleus to the contralateral lateral superior olive. On PO, ventral cochlear nucleus axons decussate in the dorsal trapezoid body, form a plexus at the dorsal edge of the contralateral medial superior olive, and enter the ventrolateral limb of the contralateral lateral superior olive. Over the next 2 weeks, fascicles of fibers form on the hilar and ventral aspects of the ventrolateral limb. Fibers arising from these fascicles form converging, but nonoverlapping, arborizations within the ventrolateral limb at right angles to the curvature of the nucleus. The medial region was devoid of labeled axons. The direct innervation of the contralateral lateral superior olive was confirmed in the adult gerbil with anterograde horseradish peroxidase histochemistry and by the recording of excitatory responses in the innervated region to acoustic stimulation of the contralateral ear. © 1995 Wiley-Liss, Inc.     

Multimodality evoked potentials in amyotrophic lateral sclerosis

Visual, brainstem auditory and somatosensory evoked potentials to medial nerve stimulation were recorded in 27 patients affected by amyotrophic lateral sclerosis. VEP N75, P100, N140, N75-P100 latencies and P100 amplitude, BAEP I-III, III-V and I-V interpeak-latencies were within normal limits in all ALS patients. Somatosensory evoked potentials were abnormally delayed in 8 patients: in 3 arms because of a delayed N9-N13 latency, in 9 arms because of a delayed N13-N19 latency.     

A case of infarction in brainstem and cerebellum as a initial symptom with bilateral hearing loss]

A 56-year old male presented with a sudden onset of bilateral hearing difficulty. He complained of dizziness and gait disturbance at the onset and subsequently developed bilateral hearing loss and tinnitus. Brain MRI revealed multiple infarcts in bilateral middle cerebellar peduncles, bilateral cerebellar hemispheres and the right cerebral peduncle. Three dimentional computed tomography angiography (3D-CTA) showed severe stenosis of bilateral vertebral arteries. Infarcts were located in the border zone between anterior inferior cerebellar artery (AICA) and superior cerebellar artery (SCA), suggesting hemodynamic infarctions. Auditory brain stem responses (ABR) were recorded three times. The initial ABR demonstrated all waves except for wave I on day 14. Wave I on the left was normal, while wave I peak latency on the right was prolonged. On day 61, all waves were recorded, although peak latencies of waves III to V and interpeak intervals of the wave I to III on the right side were prolonged. Involvements of the cochlear nerve and pontine auditory pathway were suggested from the ABR abnormalities in this case.     

Auditory brainstem response in hyperbilirubinemic rats: Part II.

The effect of an albumin-bilirubin solution on the auditory brainstem response (ABR) of rats was examined and compared with that of rats in which only bilirubin was administered. In albumin-bilirubin-loaded rats, the latencies of waves II and IV were prolonged and the amplitudes decreased, whereas the ABR wave I did not change significantly. The I-IV interpeak latency also was prolonged. These changes were more severe in rats loaded only with bilirubin. Mannitol injection hastened the appearance of ABR changes when only bilirubin was used, but peak levels of ABR changes were almost the same in the mannitol-injected groups. When the blood-brain barrier is intact, albumin administration is useful in hyperbilirubinemia for the prevention of damage to the central auditory pathways. The reversibility of the ABR changes were demonstrated in all bilirubin-administered groups.     

Sources of projections to subdivisions of the inferior colliculus in the rat

Brainstem and forebrain projections to major subdivisions of the rat inferior colliculus were studied by using retrograde and anterograde transport of horseradish peroxidase. Retrograde label from injection into the external cortex of the inferior colliculus appears bilaterally in cells of the inferior colliculus, as well as in other brainstem auditory groups including the ipsilateral dorsal nucleus of the lateral lemniscus and contralateral dorsal cochlear nucleus. The external cortex is the only collicular subdivision where an injection labels cells in the contralateral cuneate nucleus, gracile nucleus, and spinal trigeminal nucleus. Other projecting cells to the external cortex are found in the lateral nucleus of substantia nigra, the parabrachial region, the deep superior colliculus, the midbrain central gray, the periventricular nucleus, and area 39 of auditory cortex. Injection of the dorsal cortex of inferior colliculus heavily labels pyramidal cells of areas 41, 20, and 36 of the ipsilateral neocortex. Anterograde label from a large injection of auditory cortex is densely distributed in the dorsal cortex, lesser so in the external cortex, and only slightly in the central nucleus. Labelled cells appear in the central nucleus, dorsal cortex, and external cortex, primarily ipsilaterally, following dorsal cortex injection. Relatively few cells from other brainstem auditory groups show projections to the dorsal cortex. Injection of the central nucleus of the inferior colliculus results in robust labelling of nuclei of the ascending auditory pathway including the anteroventral, posteroventral, and dorsal cochlear nuclei (mainly contralaterally), and bilaterally the lateral superior olive, lateral nucleus of the trapezoid body, dorsal nucleus of the lateral lemniscus, and the central nucleus, dorsal cortex, and external cortex of the colliculus. The medial superior olive, superior paraolivary nucleus, and ventral nucleus of the trapezoid body essentially show ipsilateral projections to the central nucleus. The differential distribution of afferents to the inferior colliculus provides a substrate for functional parcellation of collicular subdivisions.     

A sexually dimorphic vasopressin innervation of auditory pathways in the guinea pig brain

Vasopressin-like immunoreactivity was detected in the auditory brainstem of female guinea pigs. Stained cell bodies and fibres were found in the inferior colliculus and in the ventral trapezoid body, and immunoreactive fibres in the dorsal cochlear nucleus. No vasopressin immunoreactivity was detected in the auditory brainstem of male guinea pigs. Using oxytocin antisera we found neither immunoreactive perikarya nor fibres in the auditory pathways of guinea pigs of both sexes.     

No auditory conduction abnormality in children with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral developmental disorder characterized by lack of sustained attention and hyperactivity. It has been suggested that asymmetrical conduction of the auditory stimulus in the brainstem plays a role in the pathophysiological process of ADHD. In the present study, the functional integrity of the central auditory pathway was assessed using the auditory brainstem response (ABR), mid-latency response (MLR) and slow vertex response (SVR). Twenty ADHD children and twenty controls were recruited for the study and recordings were done on a computerized evoked potential recorder using the 10-20 system of electrode placement. There emerged no significant difference in absolute peak latencies, interpeak latencies and amplitude of ABR or latency of MLR in the ADHD children as compared with the controls. Prolongation of the SVR latency was found in the children with ADHD versus the controls, but the difference was statistically insignificant. The present study does not suggest any auditory conduction abnormality as a contributory factor in ADHD.     

Effects of reaction time performance on single-unit activity in the central auditory pathway of the rhesus macaque

The activity of single units at various locations in the central auditory pathway of rhesus macaques was recorded during the monkeys' performance and nonperformance in an auditory reaction time task. Evoked unit responses during performance were compared with those observed during passive delivery of identical stimuli. Single units were recorded from the cochlear nucleus, superior olivary complex, lateral lemniscus, inferior colliculus, medial geniculate nucleus, and auditory cortex. Significant effects of task performance on unit discharge patterns were observed at all levels of the central auditory pathway: Spontaneous discharge rates in the more peripheral auditory nuclei tended to be higher during performance. Evoked discharge that occurred relatively late during a stimulus presentation (greater than 75 msec after stimulus onset) was increased during performance, compared with the nonperformance condition, in nuclei above the cochlear nucleus. The initial latency of evoked discharge was increased during performance for subcortical nuclei but was decreased for units in auditory cortex. These results suggest that the effects of performance may be mediated by a tonic increase in the excitability of auditory units which operates primarily at peripheral auditory stations, and a descending, stimulus-evoked increase in excitability which primarily influences the cells of higher auditory nuclei. At the cortical level, these changes lead to increased signal-to-noise ratio of the evoked response during performance in the auditory task.     

Effects of age on event-related potentials in chronic alcoholics: a multimodal study.

To test different versions of the premature aging hypothesis in alcoholics, brainstem auditory evoked potentials (BAEPs), long-latency auditory evoked potentials (LAEPs), P3 and visual evoked potentials (VEPs) were recorded in 32 alcoholic subjects. The phenomena in patients' event-related potentials (ERPs) differ from those observed in normal aging subjects and become more pronounced with age. ANOVA showed a significant effect by group (alcoholic patients/controls) on certain parameters of BAEPs (III, III-V, I-V), VEPs (P100 latency) and LAEPs (N1-P2 amplitude and N2 latency) unaffected by age, while age had a significant effect on some parameters of LAEPs (N2-P3 amplitude, P3 latency) unaffected, or less affected by chronic alcohol consumption. At a clinical level, abnormalities in BAEPs and VEPs seem good early trouble indices in alcoholic patients, while alterations in latencies and amplitudes of LAEPs appear in older patients. These data seem to be in favor of a critical age or critical abuse in the action of alcohol, in place of the classical hypothesis of premature aging.     

Longitudinal evoked potential studies in hereditary ataxias

We studied multimodal evoked potentials (EPs) longitudinally in a series of children with Friedreich's ataxia and ataxia telangiectasia to determine both their diagnostic utility and their correlation with clinical regression. The auditory brainstem responses (ABRs) were abnormal only in the children with Friedreich's ataxia. The abnormality seen in these patients was a rostral-caudal loss of the ABR waves. The visual EPs (VEPs) were abnormal in many of the patients; those with ataxia telangiectasia had unusually low amplitude or absent VEPs, occasionally with increased latencies, whereas those with Friedreich's ataxia had normal amplitude VEPs, often at increased latencies. The somatosensory EPs were usually of increased latency or absent in these patients. Unlike the ABR and VEPs, they did not serve to differentiate the groups. Changes in the EPs appeared to reflect clinical deterioration; patients with little change in their EPs over several years were regressing very slowly, whereas others had rapid deterioration in both EPs and clinical status. We suggest that the EPs are diagnostically of value in degenerative ataxias and may be of value in monitoring these patients and their response to therapy.