Auditory response of the reticular nucleus of thalamus in awake mice / 生理学报

This study aims to explore the auditory response characteristics of the thalamic reticular nucleus (TRN) in awake mice during auditory information processing, so as to deepen the understanding of TRN and explore its role in the auditory system. By in vivo electrophysiological single cell attached recording of TRN neurons in 18 SPF C57BL/6J mice, we observed the responses of 314 recorded neurons to two kinds of auditory stimuli, noise and tone, applied to mice. The results showed that TRN received projections from layer six of the primary auditory cortex (A1). Among 314 TRN neurons, 56.05% responded silently, 21.02% responded only to noise and 22.93% responded to both noise and tone. The neurons with noise response can be divided into three patterns according to their response time: onset, sustain and long-lasting, accounting for 73.19%, 14.49% and 12.32%, respectively. The response threshold of the sustain pattern neurons was lower than those of the other two types. Under noise stimulation, compared with A1 layer six, TRN neurons showed unstable auditory response (P < 0.001), higher spontaneous firing rate (P < 0.001), and longer response latency (P < 0.001). Under tone stimulation, TRN's response continuity was poor, and the frequency tuning was greatly different from that of A1 layer six (P < 0.001), but their sensitivity to tone was similar (P > 0.05), and TRN's tone response threshold was much higher than that of A1 layer six (P < 0.001). The above results demonstrate that TRN mainly undertakes the task of information transmission in the auditory system. The noise response of TRN is more extensive than the tone response. Generally, TRN prefers high-intensity acoustic stimulation.

Alteraciones neuro-funcionales en trastornos del ánimo que cursan con conductas auto-mutilatorias: estudio de perfusión regional cerebral a partir de la técnica de Neuro-SPECT Tc99-HMPAO / Neuro functional alterations in mood disorders with self-injurious behavior: study of regional cerebral perfusion through Tc-99m HMPAO NeuroSPECT

Se reportan los hallazgos encontrados a partir de NeuroSPECT en trastornos del ánimo, incluyendo trastorno bipolar, depresión mayor y auto-mutilación. Se compararon los resultados de una muestra de 29 pacientes con trastorno afectivo en espectro bipolar complicado con conductas auto-mutilatorias, un grupo de 20 pacientes bipolares sin auto-mutilación y 22 pacientes depresivos sin auto-mutilación. Dentro de los hallazgos destaca la asociación entre trastornos del ánimo y auto-mutilación con hiper-perfusión talámica bilateral en el segmento dorso-ventral-anterior, asociado a hipo-perfusión en corteza peri-límbica (áreas 32, 24 y 23 de Brodmann). Los múltiples reportes que relacionan, tanto en animales como en humanos, las conductas auto-mutilatorias con fenómenos de hipo-algesia, anestesia o disestesias, permiten hipotetizar la participación de una disfunción en circuitos tálamo-peri-límbicos asociados a vías nocioceptivas y a conciencia somato-psíquica y su relación con fenómenos auto-mutilatorios.

We report NeuroSPECT findings in mood disorders, including bipolar disorder, major depression and self-mutilation. We compare results in 29 patients with bipolar disorder complicated by self-mutilation, a group of 20 patients with bipolar disorder uncomplicated and 22 patients with mayor depression uncomplicated by self-mutilation. Among the NeuroSPECT findings we report the association of mood disorders and self-mutilation with hyperperfusion of the anterior-dorsal-ventral segment of both thalami concomitant with hypoperfusion in perilimbic cortex, namely areas 32, 24 (anterior cingulate gyrus) and 23 of Brodmann. Multiple reports in the literature relate both, in animals and man, self-mutilation with phenomena of hypoalghesia, anesthesia, or dysestesias and are the basis for our hypothesis linking dysfunction of limbic-thalamic circuits, associated with nocioceptive fibers, somato-psychic consciousness and self-mutilation phenomena.

Functional status of auditory pathways in hypothyroidism: evoked potential study.

Hypothyroidism is known to be associated with mental retardation, motor dysfunction, memory deficits and hearing impairment. In the present study, the functional integrity of the thalamocortical projections to the primary auditory cortex and association cortex has been assessed by using Auditory Evoked Responses i.e Auditory Brainstem (ABR), Mid Latency Response (MLR) and Slow Vertex Response (SVR). Thirty newly diagnosed hypothyroid patients and thirty healthy controls were taken for the study and ABR, MLR and SVR were recorded on computerized evoked potential recorder using 10-20 system of electrode placement. The second recordings for the hypothyroid patients were done 3 months after treatment with attainment of euthyroid states. The present study revealed a slight increase in absolute latency of wave III of ABR in hypothyroid patients and significant decrease in absolute latency of wave III and interpeak latency of I-III after treatment. There was a significant decrease in amplitude of wave V in hypothyroid patients and significant increase in amplitudes of ABR wave I and wave V after treatment. There was a significant increase in latency of wave Na of MLR and wave P2 of SVR in hypothyroid patients. The latencies of waves Na, Pa, Nb of MLR and waves PI and N2 of SVR showed significant improvement with thyroid hormone treatment. The results of the present study indicates that in hypothyroid state there might be slow conduction at the periphery and with treatment there is better recruitment of neuronal pool of the generators of the waves of ABR in the brainstem. We can also conclude that the thalamocortical projections of the auditory pathways are adversely affected in the hypothyroid state and this improves after treatment.

Neurobiología de las emociones / Neurobiology of emotions

Las emociones son respuestas químicas y neuronales complejas, cuya función fundamental es adaptativa. Ellas organizan tanto el pensamiento como la acción con el fin de evolucionar en vida de la manera más adecuada y óptima. Las emociones se clasifican en primarias y secundarias, siendo las primeras originadas en la amígdala y la corteza singular anterior, las que se dividen en 6 tipos universales, explicando así la similitud de la expresión emocional en todos los individuos y culturas. Las segundas se originan de preferencia en la corteza prefrontal y requieren de la cognición para desarrollarse, dándole un sello social a nuestra personalidad. El sentimiento supone un darse cuenta de las sensaciones básicas de la emoción a través de la interpretación de los cambios en el estado corporal, proceso que se realiza gracias a la integración realizada por la conciencia. En la presente revisión se detallan los mecanismos neurobiológicos y fisiológicos que determinan las diversas emociones humanas, así como las diversas estructuras cerebrales que participan en su configuración, haciendo un recorrido que abarca el binomio tálamo-amigdaliano, corteza prefrontal y hemisferios cerebrales en su rol regulatorio.

Postnatal changes of conduction velocity of the fibers in and out of the mouse barrel cortex

There are some conflicts about constancy of conduction velocity [CV] in a given tract of nervous system. By recording excitatory postsynaptic currents [EPSC] in layer IV of the somatosensory cortex we tried to clear changes in CV of thalamocortical tract of mice aged 3 to 50 days old. Field potentials and EPSC were recorded in the layer IV by stimulation of ventrobasal nucleus of thalamus [VB] and white matter [WM]. Our results indicate that in mice aged 3 through 17 days old, CV of EPSC evoked by WM and VB stimulation increased up to 2 and 15 times, respectively. Also, the data from field potentials match those from EPSC. CV enhancement of the fibers out of cortex may contribute to myelination as well as increased diameter of neurites. However, it is not the case for WM matter stimulation-evoked responses

Correlation between concomitant theta waves in nucleus reticularis pontis oralis and in hippocampus, thalamus and neocortex during dreaming in rats

Theta waves, which are the main electrophysiological expression of dreaming activity in many brain structures of rats, often undergo specific changes in voltage and frequency according to the oniric patterns. Much is known about their mechanisms but little is known regarding their origin, which has been ascribed to a specific activation of either the reticular formation or the septal nuclei or nucleus reticularis pontis oralis. In the present study, rats were prepared for chronic recording of the electro-oscillograms of cortical areas 10, 3 and 17, of hippocampal CA1 and CA3 fields, of nucleus reticularis thalami, nucleus reticularis pontis oralis and occasionally of nucleus reticularis caudalis. Head, rostrum, eye and forelimb movements were also recorded, so that the oniric behaviors could be precisely identified. The scatter diagrams and the corresponding correlation coefficients (r) of the voltage of concomitant waves were determined for each possible pair of leads. The potentials were analyzed at a frequency of 256 Hz over a period of 1 to 3 sec. A very high degree of correlation was observed between theta waves in nucleus reticularis pontis oralis, hippocampal fields and nucleus reticularis pontis caudalis; sometimes r approached unity. Although these data cannot be taken as proof of nucleus reticularis pontis oralis being the source of theta waves, they are at least compatible with this hypothesis.

Risk factors for unpleasant paresthesiae induced by paresthesiae-producing deep brain stimulation

Paresthesiae-producing deep brain stimulation (stimulation of ventrocaudal nucleus - VC, medial lemniscus - ML or internal capsule - IC) is one of the few procedures to treat the steady element of neural injury pain (NIP) currently available. Reviewing the first 60 patients with NIP submitted to deep brain stimulation (DBS) from 1978 to 1991 at the Division of Neurosurgery, Toronto Hospital, University of Toronto, we observed that 6 patients complained of unpleasant paresthesiae with paresthesiae-producing DBS, preventing permanent electrode implantation in all of them. Such patients accounted for 15 per cent of the failures (6 out of 40 failures) in our series. In an attempt to improve patient selection, we reviewed our patients considering a number of parameters in order to determine risk factors for unpleasant paresthesiae elicited by paresthesiae-producing DBS. The results showed that this response happenned only in patients with brain central pain complaining of evoked pain, secondary to a supratentorial lesion. Age, sex, duration of pain, quality of the steady pain, size of the causative lesion and site (VC,ML,IC) and type (micro or macroelectrode) of surgical exploration were not important factors. Unpleasant paresthesiae in response to dorsal column stimulation, restricted thalamic lesion on computed tomography and the occurrence of associated intermittent pain were considered major risk factors in this subset of patients and the presence of cold allodynia or hyperpathia in isolation and the absence of sensory loss were considered minor risk factors. It is our hope that the criteria here established will improve patient selection and so, the overall results of DBS.

Cortical facilitatory action on centralis lateralis thalamic activity during the development of carrageenin-produced inflammation

In order to understand the neuronal mechanisms involved in acute and chronic pain, we studied the thalamic and cortical control action, which allows the suppression of the neuronal responses to noxious stimulation. As an experimental pain model we used carrageenin injected in the paw of male Wistar rats. The tonic facilitatory cortical control on centralis lateralis thalamic nuclei (CL) activity is described at different times after carrgeenin-produced inflammation. Simultaneous extracellular unit recordings were carried out at CL and medial prefrontal cortex (PCx) cells in anesthetized male Wistar rats. The PCx control was tested by blocking in a transient and reversible manner, using the cortical spreading depression (CSD). Carrageenin injection (1 percent; 0.2 ml) into the plantar surface of the right hind paw, and the influence of Lidocaine (2 percent; 0.2 ml) applied in the inflamed paw, was tested on unit activity in PCx and CL cells. Thalamic cells recorded in acute and subacute stages (24-72 h aftercarrageenin administration) were activated by tactile, light pressure and joint movement stimulation yielded before the injection. After carrageenin, the thalamic cells displayed spontaneous high frequency burst discharges, also presenting a progressive and significant increase (p < 0.001, ANOVA test) of their spontaneous firing when rate when compared with control cell activity. Lidocaine reduced the enhanced activity induced by carrageenin in thalamic neurones (p < 0.001, Student t test). In PCx neurones were also recorded in acute and subacute stages. Cortical cells from acute and subacute group were activated by nociceptive and non-nociceptives stimulation. In acute stage, cortical cells increased their firing rate after carrageenin and we could not observe modifications upon their firing rate due to Lidocaine. The CSD blocked all cortical activity in acute subacute stages. During the CSDs, overall thalamic activity was suppressed in neurones from acute (91 percent) and subacute (87 percent) stages. The blockage was observed when the propagated weve produced by CSD arrived into the medial prefrontal cortex. the CSD also suppressed the PCx and the CL noxious responses evoked by pressure in the receptive field. This study show the tonic facilitatory control of the PCx upon intralaminar thalamic noxious responses, during acute and subsacute stages of carrageenin produced inflammation. In the literature, it has been proposed that the CL thalamic...

Potenciales corticales relacionados a movimientos en pacientes parkinsonianos sometidos a tratamiento quirúrgico neurorrestaurativo / Movement-related cortical potentials in parkinsonian patients with neurosurgical treatment

Uno de los componentes de los potenciales corticales relacionados con el movimiento, el Bereitschaft Potential (BP), se piensa que refleja la actividad preparatoria en las áreas corticales y subcorticales previas al movimiento voluntario. Estudios anatómicos han demostrado que el "output" palidal se dirige desde el tálamo al área motora suplementaria y al córtex premotor. Contrariamente el área premotora suplementaria envía un "input" hacia el pálido vía el estriado formando un "loop" anatómico entre las áreas motoras corticales y los ganglios basales. Hemos estudiado el BP en 13 pacientes parkinsonianos que fueron sometidos a diversos tratamientos neuroquirúrgicos (talamotomía, palidotomía y trasplante de tejido fetal) una semana antes y 6-8 meses después del procedimiento. Las mayores diferencias fueron observadas en el grupo de talamotomía, en relación al área entre el comienzo del BP y los 800 ms previos a la iniciación del movimiento. También observamos una correlación significativa entre esta área (800-200 ms antes del comienzo del movimiento) y la mejoría clínica en este grupo de pacientes. Estos resultados sugieren que la talamotomía podría influenciar el circuito neuronal relacionado con el BP.

Thalamic ventrobasal stimulation for pain relief: probable mechanisms, pathways and neurotransmitters

A estimulaçäo talâmica ventrobasal (VB), primeiramente realizada por Mazars em 1961, é método útil para o tratamento de dor central e dor de deaferentaçäo. A maneira como ela atua para produzir alívio da dor, porém é ainda questäo de controvérdia. Neste estudo, o autor examina as hipóteses anteriormente propostas e sugere que o alívio da dor obtido pela estimulaçäo de VB se deve a dois prováveis mecanismos: (1) Modulaçäo da atividade anormal em VB e (2) Ativaçäo de uma via multisináptica inibitória para os neurônios nociceptivos do tálamo meidal, na qual o sistema dopaminérgico nigroestriatal exerce importante papel. A via multisináptica envolvida, bem como os neurotransmissores, säo sugeridos: a estimulaçäo de VB, através da via tálamo-corticalglutaminérgica, excitaria o córtex somatosensitivo que, por sua vez, excitaria o córtex motor através dos neurotransmissores excitatórios glutamato e aspartato. No córtex sensitivo-motor se originaria a via corticoestriatal glutaminérgica excitatória para o putâmen anterior, o qual emitiria uma via peptidérgica (substância P) excitatória para o globo pálido interno (via estiatopalidal) e para a substância nigra reticulata (via estriatonigral). O globo pálido interno inibiria o tálamo medial através da via pálido-talâmica gabaérgica. A substância nigra reticulata emitiria projeçöes gabaérgicas inibitórias para o tálamo medial (via nigrotalâmica) e excitaria a substância nigra compacta. A substância nigra compacta projetaria axônios dopaminérgicos excitatórios para os neurônios estriatais com eferência para o globo pálido interno e substância nigra reticulata e assim por diante. Dados de suporte a esta hipótese säo providos por extensa revisäo da literatura

Functional characteristics (EEG) of the thalamo-telencephalic projections of toads

Electrical or chemical (carbachol) stimulation of the dorsal thalamus of anesthetized and conscious toads induced synchronization (increased number of spindles and increased amplitude of the waves) in the electric tracing (EEG) of the telencephalon. This alteration was accompanied by mydriasis and greater behavioral alert in conscious animals. No recruitment response was observed in anesthetized toads. The present findings were compared to those obtained by stimulating the nonspecific thalamus of mmmals and reptiles. Even though the data available at present do not demonstrate the existence of a system with the morphological characteristics of the reticulo-thalamo-cortical system of mammals in anurans, the functional data presented here suggest this possibility

Potenciais de latência média em indivíduos normais: estudo sobre a latência das ondas

Os autores realizaram um estudo dos potenciais de média latência em 37 indivíduos considerados normais em ambos os ouvidos, determinaram os valores médios, desvios padröes e limites de confiança para as ondas PO, Pa e Pb e fizeram consideraçöes a respeito da possível utilizaçäo clínica destes potenciais, identificaçäo de lesöes situadas nas vias auditivas do tálamo e córtex cerebral, assim como para determinaçäo de limiares auditivos de forma objetiva.

Anatomical study of the parrakeet (Aratinga canalicularis)

De estudios recientes sobre la organización del telencéfalo de las aves se sabe que esta estructura tiene muchas similitudes cocn el cerebro de los mamíferos. Tambíen se conoce que la porción del hiperestriado dorsal conocida como la wulst así cocmo la porción lateral, identificada como el lado ventricular dorsal, tiene un papel importante en la integración sensorial, el aprendizaje y la producción del canto en las aves. Aunque ambas estructuras no poseen laminación como la de la neocorteza de los mamíferos, sin embargp, ciertas aves como el búho muestran una clara pseudolaminación. En la literatura no hay descripciones anatómicas de la wulst en preicos, por lo que el objetivo del presente trabajo fue estudiar esta estructura en la ewpecie. Aratinga canicularis. Se identificaron tres tipos celulares y, mediante métodos morfométricos efectuados en un total de 240 células por cada estrato, se midieron 10 parámetros distintos y se distinguieron tres estratos, a los que se les denominó dorsal, medial y ventral. Cada uno de los tres tipos celulares presentaron características específicas. Las células multipolares y triangulares mostraron un patrón dendrítico ramificado y abundantes espinas dendríticas. Las triangulares difieron en cuanto a la extensión de sus dendritas y la ramificación de su axón en ángulos rectos dirigidos hacia el estrato suprayacente. Las células ovoides fueron las mas pequeñas con pocas ramas y espinas. Estas células son similares a las del hiperestriatum accesorio del buho, las que a su vez son análogas a las células granulares de la corteza visual de los mamíferos

Papel del complejo pulvinar-lateral posterior en la respuesta de rotación: relación con otras estructuras cerebrales; sistemas farmacológicos implicados en esta conducta / Role of pulvinar lateralis posterior complex on rotation response: relation with other cerebral structures; pharmacological systems involved in this behavior

Se hace un análisis crítico de los resultados obtenidos en 4 series experimentales efectuadas en gatos. En estos experimentos se muestran los resultados siguientes: 1) la estimulación eléctrica del completo pulvinar-lateral posterior (P-LP) evoca ratación contralateral de la cabeza, acompañada de una rotación de ambos ojos en la misma dirección, la mayor parte de las veces de tipo sacádico. Con intensidades de corriente superior se produce rotación contralaterl de todo el cuerpo; 2) las eferencias desde el P-LP para producir estos efectos se hacen a través del colículo superior ipsilateral. La lesión electrolítica de esta última estructura suprime la conducta de rotación inducida por estimulación elétrica del P-LP. Este resultado no se obtiene cuando es lesionado el núcleo causado o el centralis later alis; 3) la ablación de la corteza cerebral ipsilateral, que tiene conexiones recíprocas importantes con el P-LP. produce la supresión de la respuesta de rotación en el 50 % de los gatos en la primeira semana que sigue a la resección cortical. Sin embargo, 30 días después de la ablación, el 86 % de los electrodos implantados en en P-LP son capaces de inducir, por estimulación elétrica, la respuesta de rotación, y 4) la inyección local en el P-LP a través de una cánula de carbacol o dioxolano, este último activador exclusivo de los receptores muscarínicos, produce también respuesta de rotación contralateral de cabeza-ojo-cuerpo. Los resultados expuestos nos permiten postular que el P-LP es otra estructura cerebral relacionada con rotación y diferente del sistema nigro-estriatal. Este último no es afectado por lesión del colículo superior, como sucede con el P-LP. Por otra parte, el neurotransmisor más importante implicado en la conducta de rotación en el sistema nigro-estriatal es la dopamina, en tanto que en el P-LP es la acetilcolina

Arrest reaction with concomitant spike and wave afterdischarge following thalamic stimulation in conscious juvenile monkeys with Al (OH)3 focal premotor lesions.

The behavioural and electroencephalographic responses resulting from stimulation of a specific area in the nucleus medialis dorsalis (nMD) of unanaesthetized juvenile Rhesus monkeys is described. A behavioural arrest reaction, lack of awareness and motor inhibition with concomitant 2 1/2 to 3Hz spike and wave EEG afterdischarge patterns were obtained by stimulation of the nMD in monkeys with bilaterally symmetrical aluminium hydroxide Al (OH)3 lesions in anterior premotor cortical areas.

Experimental spike and wave EEG pattern from thalamic stimulation in anaesthetized juvenile monkeys.

A bilaterally synchronous 3/sec spike and wave pattern in the EEG can be obtained during stimulation of the nucleus medialis dorsalis (nMD) and nucleus paracentralis (nPC) of the thalamus, in lightly anaesthetized juvenile monkeys. The spike and wave EEG patterns have a frequency of 2 1/2 to 3Hz and occur during low frequency stimulation, without continuing into the post-stimulatory phase. Stimulation of the mesencephalic reticular formation (MRF) at higher voltages inhibits the thalamic-induced spike and wave response. This finding has heuristic significance, as activating stimuli arrest the wave and spike EEG pattern of human absence (petit mal epilepsy) seizures. The study also demonstrates the morphological similarity of the 3/sec spike and wave thalamic induced response in experimental and clinical absence states as well as similarities in their alterations with different levels of activation.