Ismael Mena

Functional studies of the human auditory pathway after monaural stimulation with pure tones. Establishing a normal database

Conclusions Bilateral activation of Brodmann area 39 provides functional support for the concept of bilateral cortical activation with auditory stimulation. The observation that when Brodmann area 39 is activated, area 38 of the temporal lobe is simultaneously inhibited (a functional observation that has seemingly not been previously reported) supports the concept that inhibitory as well as excitatory relays play a role in the auditory pathways. In addition, this report helps to establish a functional database for future studies. Objectives (i) To determine which areas of the cerebral cortex and basal ganglia are activated when the left and right ears are monaurally stimulated with pure tones, and what type of response (e.g. excitatory or inhibitory) occurs in these different areas. (ii) To determine the degree of ipsi- and/or contralateral cortical activation and/or inhibition depending on the ear that is stimulated. (iii) To use this information as an initial step to develop a normal functional database for future studies. Material and methods A brain perfusion single-photon emission CT (SPECT) evaluation was conducted using auditory monaural stimulation with pure tones in 10 normal volunteers. Both ears were tested independently (20 examinations in total). 99mTc hexamethyl-propylenamine-oxime was injected while pure tones were delivered, and the SPECT imaging was done 1 h later. Results After delivering pure tones there was bilateral cortical activation in Brodmann areas 39 and 40, regardless of which ear was stimulated. Despite marked hyperperfusion in both areas 39, a more intense response was seen on the left compared to the right side, although this was not statistically significant. There was also activation in the executive frontal cortex areas 9 and 10 as well as in the temporal Brodmann areas 21 and 22. Simultaneously, area 38 of the temporal lobe was deactivated. In the subcortical structures there was also marked activation in both thalami and deactivation of the caudate nuclei without lateralization.

Spontaneous musical auditory perceptions in patients who develop abrupt bilateral sensorineural hearing loss. An uninhibition syndrome

Conclusions. Spontaneous musical auditory perceptions commonly occur in patients who develop abrupt bilateral sensorineural hearing loss. The findings in both subjects who were image tested while having these perceptions are suggestive of a biological substrate for this process and of a central locus for auditory memory seemingly located in and around area 39 of Brodmann. When an individual has abrupt bilateral sensorineural hearing loss, stored musical memory can be released and this person can have musical perceptions without an external source. It is likely that an abrupt bilateral loss of inner ear function might uninhibit neuronal groups storing auditory memory. Objectives. The objectives of this study were as follows. (1) To determine if spontaneous musical auditory perceptions occur in patients who develop abrupt bilateral severe sensorineural hearing loss (not necessarily simultaneously). (2) To determine if there is a biological substrate to the process of recalling previous auditory perceptions. (3) To compare these findings with our normal databases of unstimulated and pure tone-stimulated volunteers. (4) To establish a hypothesis for the mechanisms of these occurrences. Patients and methods. Thirty two patients who had had abrupt bilateral severe sensorineural hearing loss (the interval between the losses of both ears could have been years) were contacted. They were asked if they had ever had the sensation of having musical auditory perceptions without external auditory stimuli. Two of these patients were image tested with single photon computerized emission tomography (neuroSPECT) while they were having these perceptions. Results. All of the 32 subjects had musical auditory perceptions following their hearing loss in the second ear or when hearing loss in both ears occurred simultaneously. The two patients who were image tested with neuroSPECT had similar findings. There was a statistically significant increase in perfusion in area 39 of Brodmann, more intense on the right side, with increased perfusion also in both frontal lobes at the middle gyrus, with bilateral hypoperfusion in area 38 of Brodmann. These findings are similar to those observed in normal volunteers stimulated with pure tones.

Musical brains: a study of spontaneous and evoked musical sensations without external auditory stimuli.

Conclusions. Our observations confirm that musical sensations with no external stimuli, either spontaneous or evoked, occur in normal individuals and that a biological substrate can be demonstrated by brain single photon emission computed tomography (SPECT). Objectives. There are individuals, usually musicians, who are seemingly able to evoke and/or have spontaneous musical sensations without external auditory stimuli. However, to date there is no available evidence to determine if it is feasible to have musical sensations without using external sensory receptors, or if there is a biological substrate for these sensations. Subjects and methods. A group of 100 musicians and another of 150 otolaryngologists were asked if they had spontaneous musical auditory sensations and/or were capable of evoking them. SPECT evaluations with Tc99m-HMPAO were conducted in six female musicians while they were evoking these sensations or, in one case, while she was having them spontaneously. In three of them an additional SPECT was conducted in basal conditions (having been asked to avoid evoking music).Results. In all, 97 of 100 musicians had spontaneous musical sensations; all 100 could evoke and modify them. Of the 150 otolaryngologists, 18 (12%) were musicians. Of the 132 nonmusicians, spontaneous musical sensations occurred in 52 (39.4%), 72 (54.5%) could evoke and 23 (17.4%) were able to modify them, 58 (43.9%) did not have spontaneous musical sensations nor could they evoke them. The musical sensations of the 72 otolaryngologists that could evoke were less elaborated than those of musicians. NeuroSPECT during voluntary musical autoevocation demonstrated significant (>2 SD) increased activation of executive frontal cortex in Brodmann areas 9 and 10, secondary visual cortex (area 17), and paracingulate (areas 31 and 32). There was also activation in the para-executive frontal cortex (areas 45 and 46). In the basal ganglia there was activation in thalamus and lentiform nucleus. Deactivation below 2 SD was demonstrated by mean values in the cingulate gyrus, Brodmann areas 23 and 24, and subgenual area 25. Deactivation was also demonstrated when minimal values were analyzed in the same areas plus area 4 and areas 36 and 38, the latter in the pole of the temporal lobes. In three patients comparison of basal state with autoevocation demonstrated activation in executive frontal cortex (areas 8 and 9), para-executive cortex (area 45), primary auditory cortex (area 40), the right thalamus, and lentiform nucleus.

Efectos del consumo de marihuana en escolares sobre funciones cerebrales demostrados mediante pruebas neuropsicológicas e imágenes de neuro-SPECT

SUMMARY Comparative study based on 565 adolescent school children coming from four schools in the metropolitan area of Santiago, Chile. All were interviewed in order to select a sample that was stratified for sex, class and condition of consumer or non-consumer. The variables of intellectual coefficient and socioeconomical level were maintained constant. With this selection we conformed two groups: 40 consumers exclusively of marihuana and 40 non-consumers. We compared the results obtained in both groups in the neuropsychological tests while the neuroSPECT studies of consumers were compared against a normal database for the same age group. The adolescent consumers of marihuana demonstrate less cognitive capacity related to the process of learning such as attention, concentration, ranking, viso-spatial integration, immediate retention and visual memory. The differences between both groups are statistically significant. The findings of neuroSPECT demonstrate subgenual hypoperfusion bilaterally, more marked on the left side, in area 25 of Brodmann. This area controls mood. There is also frontal bilateral hypoperfusion (area 10 and area 32 of Brodmann). Area 32 is pre-anterior cingulate gyrus. Also hypoperfusion of the anterior cingulate gyrus (area 24 of Brodmann) and hypoperfusion of area 36 of Brodmann that projects over the hippocampus. Students that were consumers exclusively of marihuana demonstrate coincident abnormal findings of neuroimages and neuropsychological tests in areas of the brain related with learning and also significant differences between consumers with non-consumers in the neuropsychological tests.

Functional studies (NeuroSPECT) of the human auditory pathway after stimulating binaurally with pure tones

Abstract Conclusions: Our observations support the concept of bilateral cortical activation with monaural and binaural auditory stimulation. The observation that most of the significantly activated areas were the same with monaural or binaural stimulation suggests that the differences in auditory perception with binaural stimulation are not due to the involvement of significantly different processing centers but, more likely, to the type of information that reaches these centers for processing. The observation that the degree of stimulation was less intense in binaural than in monaural stimulation supports the concept that a richer binaural auditory stimulation compared with monaural stimulation does not mean summation of stimuli but integration and better processing of the information. For normal bilateral hearing subjects, a monaural stimulus is an uncommon event and may thus explain the more intense response. The repeatability of the results for monaural and binaural stimulation with pure tones in the same subjects confirms the consistency of the testing method. Objectives: (1) To determine which areas of the cerebral cortex and basal ganglia are activated by binaural stimulation with pure tones (left and right ear simultaneously) and what type of response occurs (e.g. excitatory or inhibitory) in these different areas. (2) To determine the degree of ipsilateral and/or contralateral cortical activation and/or inhibition. (3) To compare the data with our previous reports of monaural stimulation using the same technique and the same subjects. (4) To evaluate the consistency of our testing method. Methods: Brain perfusion single photon emission computed tomography (SPECT) evaluation was conducted using auditory binaural stimulation with pure tones in six normal volunteers. Both ears were stimulated simultaneously. Tc99m HMPAO was injected while pure tones were delivered and the SPECT imaging was done 1 h later. Results: After delivering pure tones there was bilateral activation in Brodmann areas 7 (somatosensory association cortex), 9 and 10 (executive frontal areas), 17, 18, and 19 (associative visual cortex). There was also activation in temporal areas 21, 22 (auditory association areas), and parietal areas 39 and 40 (Wernicke). There was also marked activation in both thalami. These activated areas were the same as those in our previous reports with monaural stimulation in the same subjects. However, except for areas 17, 18, 23, 31, and 32 (which remained over 4 SD above the normal maximum), the degree of activation was less intense in binaural compared with monaural stimulation. Inhibition was also less intense in binaural stimulation.

Is there a difference in activation or in inhibition of cortical auditory centers depending on the ear that is stimulated

Conclusions.1.With auditory stimuli cortical activation of Brodmanns areas 39 and 40 and inhibition of area 38 is bilateral. Inhibitory and excitatory relays play a role in the auditory pathways. 2. A statistically significant increased activation on the left side in areas 39 and 40, regardless of the stimulated ear, is suggestive that pure tones are preferably processed in the left hemisphere. 3. The significant difference in central inhibition depending on which ear is stimulated is supportive of the idea of a leading ear. Objectives: The objectives were to determine cortical activation/inhibition, ipsi/contralateral in response to monaural stimulation with pure tones, and if the response differs for right/left ear stimulation. Subjects and methods: Tc99m-HMPAO brain perfusion SPECT was done during monaural stimulation with pure tones in 10 volunteers. Ears were tested independently. Results: During auditory stimulation perfusion increased in both hemispheres in Brodmanns areas 39–40 and decreased in area 38,>2 SD above and below the normal mean respectively, in both hemispheres, regardless of which side was stimulated. A significantly more intense response was seen in left versus right in areas 39 and 40. In area 38 there was bilateral inhibition, significantly more intense in response to left than right ear stimulation.