Aportes sobre el correlato neuroanatómico de la personalidad / Contributions on neuroanatomical correlate of personality

Concept of personality is refers to stable and relevant attributes of a person, that explain consistent behavior patterns. Many researchers have different brain areas involved in controlling personality. Several highlighted the role of the orbitofrontal cortex in the ability to reverse the association between stimulus and reinforcement, others associated it later with the prediction ofsensory events subsequent results. The medial frontal cortex has been involved with functions as the control of actions, monitoring results as punishments and rewards, personal perception of stimuli and social cognition. Others include the lateral prefrontal cortex in complex issues of valuation. Finally, the anterior temporal region is considered to be related with facial recognition and social knowledge. In this paper we review evidence available in today’s literature about the neuroanatomical substrate ofpersonality, and its application to the study of two disorders: psychopathy and borderline personality disorder. Understanding this substrate could mean a contribution for treatment.

La personalidad corresponde a aquellos atributos estables y relevantes de una persona, que explican patrones consistentes de comportamiento. Muchos investigadores han implicado distintas áreas cerebrales en el control de la personalidad. Varios destacaron el papel de la corteza orbitofrontal en la capacidad de revertir la asociación estímulo refuerzo y posteriormente en la predicción de resultados posteriores a eventos sensoriales. Se ha involucrado a la corteza medial frontal en funciones como el control de las acciones, el monitoreo de resultados como castigos y recompensas, la percepción personal de estímulos y la cognición social. Otros incluyen a la corteza prefrontal lateral en aspectos complejos de la valoración. Por último, se considera a la región temporal anterior en el reconocimiento facial y también en el conocimiento social. En la presente revisión se expone parte de la evidencia disponible en la actualidad en la literatura, acerca del sustrato neuroanatómico de la personalidad y su aplicación al estudio de dos patologías: la psicopatía y el trastorno limítrofe. La comprensión de este sustrato puede significar un aporte para el tratamiento.

Análisis neuroforense de la violencia: propuesta de revisión / Neuroforensic analysis of violence: proposed revision

Frente a la conducta homicida se presenta una diferenciación de posiciones biologicistas que relacionan la pauta homicida con factores filogenéticos y posibles daños en funciones neuropsicológicas complejas principalmente relacionadas con el control consciente de la conducta y la planeación. El planteamiento neuropsicológico relaciona el funcionamiento del cerebro con el comportamiento homicida principalmente con alteraciones en funciones ejecutivas y de planeación relacionadas con el lóbulo frontal, así como con alteraciones en el cuerpo calloso, la amígdala, el tálamo y alteraciones en la región medial de los lóbulos temporales...

Facing homicidal behavior differentiation biologicist positions relating to phylogenetic pattern homicidal factors and possible damage to complex neuropsychological functions related primarily conscious control of behavior and planning is presented. Neuropsychological approach to brain function related to homicidal behavior primarily with changes in executive and planning related to the frontal lobe functions, as well as alterations in the corpus callosum, amygdala, thalamus and alterations in the medial lobes temporary...

Estructuras cerebrales implicadas en el procesamiento temporal / Brain structures involved in temporal processing

El tiempo siempre ha sido una constante regulatoria del comportamiento humano. Durante las últimas dos décadas, la neurociencia ha buscado las bases biológicas al igual que la localización específica de estructuras o sistemas que el cerebro humano utilice en la ejecución, interpretación o retención de procesamientos temporales. La presente revisión reúne gran parte de los estudios actuales enfocados en la ubicación de las estructuras que involucran lapsos de retención, cronometraje o procesamiento temporal, reportando evidencia respecto a diversas estructuras involucradas, como lo son los ganglios basales; en la activación del putamen respecto a conteos dentro de respuestas motoras; Al cerebelo, en relación a intervalos de duración relativamente breves de tiempo, que van desde 300, 400, 600 y 800 ms, hasta 1-2 o 12-24 segundos; En la relación entre amígdala y corteza insular, en la ejecución de cronometraje controlado; En corteza frontal/pre-frontal, asociado a períodos breves (menores a 1 s) o al menor rendimiento de procesos atencionales o de memoria, propios del funcionamiento ejecutivo; y corteza parietal, asociada a la comparación consiente de las duraciones en rango de segundos (intervalos de 1 s) en relación a señales auditivas y visuales, así como en la codificación espacial y el procesamiento de cantidades numéricas. La localización de estas estructuras es la base para el desarrollo de modelos de estudio e integración de sistemas cada vez más precisos respecto a cómo el cerebro humano interpreta el tiempo...

Time has always been a constant regulatory human behavior. During the past two decades, neuroscience has sought the biological basis as the specific location of structures or systems that use the human brain in the execution, interpretation or retention of time processing. The present revision gathers much of the current research focused on the location of structures that involve retention periods, timing or temporal processing, reporting evidence regarding various structures involved, such as the basal ganglia, in the putamen regarding activation counts within motor responses; The cerebellum, in relation to a relatively short duration intervals of time, ranging from 300, 400, 600 and 800 ms, 1-2 or 12-24 seconds; In the relationship between amygdale and insular cortex, in performing timing control; In frontal/prefrontal cortex, associated with brief periods (less than 1-s) or lower yield of attention or memory processing, typical of executive functioning; And parietal cortex associated consents comparison of durations in seconds range (1-s intervals) in relation to auditory and visual cues, as well as spatial encoding and processing numerical quantities. The location of these structures is the basis for the development of study models and integration systems increasingly accurate as to how the human brain interprets the time...

Procesamiento emocional en la vejez / Emotional processing in old age

Se cita la etimología de la palabra emoción, la evolución histórica de las diferentes teorías de esta y se profundiza en la Teoría de las emociones de A. Damasio, quien clasifica las emociones como: de fondo, primarias y secundarias, describe el procesamiento emocional, diferencia y define emoción de sentimiento. El planteo es ¿procesan igual las emociones los adultos mayores que los jóvenes?, si fuera así, ¿qué beneficios les traería? Se revisaron trabajos neurobiológicos que muestran un mejor procesamiento de las emociones positivas que de las negativas en la vejez sana a través de estudios con RMCf (Resonancia Magnética de Cerebro funcional). Se cita la Teoría de la selectividad socioemocional. En 1993, L. Carstensen postula que con el envejecimiento se produce un cambio motivacional por el cual las personas jerarquizan las metas, su significado y la optimizacion de su experiencia. Frente a eventos vitales negativos (enfermedades, pérdidas afectivas, etc. las personas mayores siguen manteniendo niveles similares o superiores de bienestar subjetivo es la Paradoja del bienestar en la vejez. Se analizan trabajos sobre emociones y enfermedad de Alzheimer.

The etymology of the word "emotion" is explained as well as its evolution throughout the years. Antonio Damasio's classification of backgrounds, primary and secondary emotions are described along with its differences in moaning with the word "feeling". Two differences in emotional Procedure between older and young adults are mentions. RMCf was shown a better positive emotional processing in old age. From Social Theories, Selectivity, Hierarchical organization of goals, paradox in the elderly, emotional balance, and subjective dimensions and shown. The relationship between these change and life quality during normal and pathological aging as well as Alzheimer's disease is also mentions.

The influence of stress on fear memory processes

It is well recognized that stressful experiences promote robust emotional memories, which are well remembered. The amygdaloid complex, principally the basolateral complex (BLA), plays a pivotal role in fear memory and in the modulation of stress-induced emotional responses. A large number of reports have revealed that GABAergic interneurons provide a powerful inhibitory control of the activity of projecting glutamatergic neurons in the BLA. Indeed, a reduced GABAergic control in the BLA is essential for the stress-induced influence on the emergence of associative fear memory and on the generation of long-term potentiation (LTP) in BLA neurons. The extracellular signal-regulated kinase (ERK) subfamily of the mitogen-activated protein kinase (MAPK) signaling pathway in the BLA plays a central role in the consolidation process and synaptic plasticity. In support of the view that stress facilitates long-term fear memory, stressed animals exhibited a phospho-ERK2 (pERK2) increase in the BLA, suggesting the involvement of this mechanism in the promoting influence of threatening stimuli on the consolidation fear memory. Moreover, the occurrence of reactivation-induced lability is prevented when fear memory is encoded under intense stressful conditions since the memory trace remains immune to disruption after recall in previously stressed animals. Thus, the underlying mechanism in retrieval-induced instability seems not to be functional in memories formed under stress. All these findings are indicative that stress influences both the consolidation and reconsolidation fear memory processes. Thus, it seems reasonable to propose that the emotional state generated by an environmental challenge critically modulates the formation and maintenance of long-term fear memory.

What ethologically based models have taught us about the neural systems underlying fear and anxiety

Classical Pavlovian fear conditioning to painful stimuli has provided the generally accepted view of a core system centered in the central amygdala to organize fear responses. Ethologically based models using other sources of threat likely to be expected in a natural environment, such as predators or aggressive dominant conspecifics, have challenged this concept of a unitary core circuit for fear processing. We discuss here what the ethologically based models have told us about the neural systems organizing fear responses. We explored the concept that parallel paths process different classes of threats, and that these different paths influence distinct regions in the periaqueductal gray - a critical element for the organization of all kinds of fear responses. Despite this parallel processing of different kinds of threats, we have discussed an interesting emerging view that common cortical-hippocampal-amygdalar paths seem to be engaged in fear conditioning to painful stimuli, to predators and, perhaps, to aggressive dominant conspecifics as well. Overall, the aim of this review is to bring into focus a more global and comprehensive view of the systems organizing fear responses.

The neurobiology of infant maternal odor learning

Infant rats must learn to identify their mother’s diet-dependent odor. Once learned, maternal odor controls pups’ approach to the mother, their social behavior and nipple attachment. Here we present a review of the research from four different laboratories, which suggests that neural and behavioral responses to the natural maternal odor and neonatal learned odors are similar. Together, these data indicate that pups have a unique learning circuit relying on the olfactory bulb for neural plasticity and on the hyperfunctioning noradrenergic locus coeruleus flooding the olfactory bulb with norepinephrine to support the neural changes. Another important factor making this system unique is the inability of the amygdala to become incorporated into the infant learning circuit. Thus, infant rats appear to be primed in early life to learn odors that will evoke approach responses supporting attachment to the caregiver.

GABA in the central amygdaloid nucleus modulates the electrolyte excretion and hormonal responses to blood volume expansion in rats

We investigated the involvement of GABAergic mechanisms of the central amygdaloid nucleus (CeA) in unanesthetized rats subjected to acute isotonic or hypertonic blood volume expansion (BVE). Male Wistar rats bearing cannulas unilaterally implanted in the CeA were treated with vehicle, muscimol (0.2 nmol/0.2 µL) or bicuculline (1.6 nmol/0.2 µL) in the CeA, followed by isotonic or hypertonic BVE (0.15 or 0.3 M NaCl, 2 mL/100 g body weight over 1 min). The vehicle-treated group showed an increase in sodium excretion, urinary volume, plasma oxytocin (OT), and atrial natriuretic peptide (ANP) levels compared to control rats. Muscimol reduced the effects of BVE on sodium excretion (isotonic: 2.4 ± 0.3 vs vehicle: 4.8 ± 0.2 and hypertonic: 4.0 ± 0.7 vs vehicle: 8.7 ± 0.6 µEq·100 g-1·40 min-1); urinary volume after hypertonic BVE (83.8 ± 10 vs vehicle: 255.6 ± 16.5 µL·100 g-1·40 min-1); plasma OT levels (isotonic: 15.3 ± 0.6 vs vehicle: 19.3 ± 1 and hypertonic: 26.5 ± 2.6 vs vehicle: 48 ± 3 pg/mL), and ANP levels (isotonic: 97 ± 12.8 vs vehicle: 258.3 ± 28.1 and hypertonic: 160 ± 14.6 vs vehicle: 318 ± 16.3 pg/mL). Bicuculline reduced the effects of isotonic or hypertonic BVE on urinary volume and ANP levels compared to vehicle-treated rats. However, bicuculline enhanced the effects of hypertonic BVE on plasma OT levels. These data suggest that CeA GABAergic mechanisms are involved in the control of ANP and OT secretion, as well as in sodium and water excretion in response to isotonic or hypertonic blood volume expansion.

Estudio mediante imagen funcional de resonancia magnética (fMRI) de las activaciones emotivas correlacionadas a la presentación de rostros extraños o del propio rostro en sujetos con personalidad inward y outward / Functional magnetic resonance imaging (fMRI) study of emotional expressions correlated to strange face expressions or of the itself in subjects with inward or outward personality

Introduction: Due to patterns ofreciprocity based on steady and coherent behaviours or, on the contrary, on articúlate and changing behaviours, attachment relationships produce personal meaning organizations respectively centred on inward or outward focus. In inward organizations, emotions are more distinct and reciprocity is more based on physical distance (protection, loneliness); in outward organizations, emotions are more blurred and reciprocity is more based on a semantic sight of relations (approval, rules). Thanks to the modern technologies of neuroimaging (especially functional magnetic resonance, flMR), a scientific, Uve study ofwhat happens when an emotion starts is now possible. Method: We studied in 10 healthy subjects the amygdala and other nervous system structures activations when the subject perceives emotional expressions by seeing an unknown face and his/her own face. Results were also matched with inward/outward organization (studied with clinical approach and MMPI2, QSP, MQOP). Results and Discussion: Our results proved that an unknown face produces higher activation on the subjects than their own face (surprise effect); the anger mostly activates the right amygdala, while the joy activates both the amygdalas or the left one (it produces a semantic decoding). Outward subjects, with respect to the inward ones, respond to the anger with a less intense and univocal pattern, actívate more cortical ßreas, not always respond to their own facial expressions and respond to the joy with an higher involvement ofthe left verbal hemisphere.

Introducción: Patrones de reciprocidad estable y coherente o, al contrario, no unívocos y cambiantes, permiten desarrollar organizaciones de significado personal con enfoque de la experiencia a lo interno (inward) o externo (outward). En los inward las emociones son más definidas y la reciprocidad es primordialmente física (protección, soledad); en los outward las emociones son más difuminadas y la reciprocidad es prevalentemente semántica (confirmación, reglas). Las modernas tecnologías de imágenes funcionales han permitido estudiar en vivo qué sucede cuando se experimenta una emoción. Método: Hemos estudiado, mediante imagen funcional de resonancia magnética (fMRI), las activaciones de la amígdalay de otras estructuras del SNCproducidas, en 10 voluntarios sanos, por estímulos emocionales externos estandarizados, tanto cuando el sujeto percibe expresiones emotivas relativas a un rostro extraño (tercera persona), como relativas al rostro propio (primera persona). Resultados y Discusión: Los resultados obtenidos han sido confrontados con las modalidades de enfoque inward o outward, atribuibles al funcionamiento de base de la personalidad individual. Tales modalidades han sido comprobadas mediante MMPI2, QSPyMQOP asociados a una evaluación clínica realizada por un psicoterapeuta experto. Los resultados indican que un rostro extraño produce activaciones mayores respecto al propio (efecto sorpresa), que la rabia activa mayormente la amígdala derecha, mientras que la alegría activa ambas amígdalas o la izquierda. Los outward, respecto a los inward, responden a la rabia de manera menos intensa y unívoca, activan más áreas corticales, pueden no responder a las emociones propias y tienen una mayor implicación del hemisferio verbal en la alegría.

As bases neuroanatômicas do comportamento: histórico e contribuições recentes / Neuroanatomical basis of behavior: history and recent contributions

Tendo em vista as mais recentes contribuições, as áreas corticais límbicas - originalmente denominadas em conjunto de grande lobo límbico -, além dos giros do cíngulo e parahipocampal, são constituídas pelas regiões mais posteriores do córtex fronto-orbitário e pelo córtex insular. Em contraposição ao restante do córtex cerebral, que se projeta sobre os gânglios da base (particularmente sobre as porções mais dorsais e mais extensas do striatum, constituídas fundamentalmente pelo núcleo caudado e pelo putame), as áreas corticais límbicas se caracterizam por se projetarem principalmente sobre o hipotálamo e também sobre a porção mais ventral do striatum (principalmente sobre o núcleo accumbens). Uma vez que todo o striatum se projeta para o globo pálido - e este para o tálamo, que se projeta para o córtex cerebral, constituindo-se, assim, circuitos córtico-subcorticais reentrantes -, tem-se que, enquanto as alças relacionadas com o striatum e o pallidum dorsais são responsáveis por atividades e rotinas motoras, as alças relacionadas com o striatum e o pallidum ventrais caracterizam circuitos córtico-subcorticais reentrantes e segregados que se relacionam particularmente com funções comportamentais. A amígdala estendida (amígdala centromedial, componente dorsal ou estria terminal, componente ventral e núcleo da estria terminal), por sua vez, também recebe aferências de todas as áreas corticais límbicas, é particularmente modulada pelas áreas corticais pré-frontais e, ao invés de se projetar sobre o striatum, projeta-se diretamente sobre o hipotálamo e o tronco encefálico. Ao receber também conexões diretas do tálamo, a amígdala estendida pode ainda desencadear respostas principalmente autonômicas, de forma inespecífica, porém rápida, através da ativação de centros do tronco encefálico. Os sistemas macro-anatômicos fronto-basais, estriatal-palidal ventral e amígdala estendida, em conjunto com o núcleo basal de Meynert e com o sistema septo-banda...

Considering the most recent contributions, the limbic cortical areas, originally known as the greater limbic lobe, besides the cingulated and the parahippocampal gyri also includes the insula and the posterior orbital cortex. In contrast to the nonlimbic cortical areas that project to the basal ganglia (particularly over the dorsal aspects of the striatum, constituted by the caudate nucleus and by the putamen), the limbic cortical areas are characterized by projecting to the hypothalamus and also to the ventral striatum (particularly to the nucleus accumbens). Once all the striatum projects to the globus pallidus which projects to the thalamus and then to the cortex, generating cortical-subcortical reentrant circuits, while the dorsal striatum and pallidum related cortico-subcortical loops are involved with motor activities, the ventral cortical-striatal-pallidal system is particularly related with behavior functions. The extended amygdala (central medial amygdala, stria terminalis or dorsal component, ventral component, and bed nucleus of stria terminalis) receives inputs primarily from the limbic cortical areas, is particularly modulated by the prefrontal cortex, and receives also direct connections from the thalamus that enables the amygdala to generate nonspecific and quick responses through its projections to the hypothalamus and to the brainstem. The ventral striatal-pallidal and the extended amygdala are then two basal forebrain macro-anatomical systems, that together with the basal nucleus of Meynert and with the septal-diagonal band system, constitute the main structures that are particularly connected with the limbic cortical areas, and that altogether project to the hypothalamus and to the brainstem which give rise to the autonomic, endocrine and somatosensory components of the emotional experiences, and that regulate the basic activities of drinking, eating, and related to the sexual behavior.

Brain areas activated after ejaculation in healthy young human subjects.

Brain mechanisms for the refractory period that characteristically follows ejaculation in animals and human are poorly understood. The possibility of active inhibition of brain areas being responsible for the post-ejaculatory inhibitory state has not been ruled out. Using Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) we have mapped brain areas in healthy young volunteers immediately after ejaculation. Functional imaging of the brain for 30 minutes beginning after three minutes of ejaculation induced by masturbation showed spatio-temporal activation in amygdala, temporal lobes and septal areas. The septal areas were observed to be active for a shorter duration than the amygdala and the temporal lobe. Thus the temporal sequence of involvement of the above neural structures may contribute to temporary inhibition of sexual arousal/penile erection during the post-ejaculatory refractory period in humans.

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.

Amygdalar neuronal responses to peripheral nociceptive stimuli in rats.

Amygdala plays a very important role in the mediation of pain. In the present study the behaviour of the amygdalar neurons in response to various peripheral noxious stimuli was observed. Noxious mechanical, thermal, electrical, chemical and the non-noxious stimuli (touch) were applied individually to the animal and then the neuronal responses to these stimuli were recorded. Our results showed that the majority of amygdalar units recorded from medial, lateral and basolateral nuclei, responded to different peripheral noxious (thermal, electrical, chemical mechanical) and non-noxious stimuli by excitation. However few neurons decreased their activity on stimulation. Some of these neurons also exhibited after discharge following application of higher intensity of noxious stimuli.

The inactivation of the basolateral nucleus of the rat amygdala has an anxiolytic effect in the elevated T-maze and light/dark transition tests

Pharmacological evidence indicates that the basolateral nucleus of the amygdala (BLA) is involved in the mediation of inhibitory avoidance but not of escape behavior in the elevated T-maze test. These defensive responses have been associated with generalized anxiety disorder (GAD) and panic disorder, respectively. In the present study, we determined whether the BLA plays a differential role in the control of inhibitory avoidance and escape responses in the elevated T-maze. Male Wistar rats (250-280 g, N = 9-10 in each treatment group) were pre-exposed to one of the open arms of the maze for 30 min and 24 h later tested in the model after inactivation of the BLA by a local injection of the GABA A receptor agonist muscimol (8 nmol in 0.2 æL). It has been shown that a prior forced exposure to one of the open arms of the maze, by shortening latencies to withdrawal from the open arm during the test, improves the escape task as a behavioral index of panic. The effects of muscimol in the elevated T-maze were compared to those caused by this GABA agonist in the avoidance reaction generated in the light/dark transition test. This defensive behavior has also been associated with GAD. In the elevated T-maze, intra-BLA injection of muscimol impaired inhibitory avoidance (control: 187.70 ± 14.90 s, muscimol: 37.10 ± 2.63 s), indicating an anxiolytic effect, without interfering with escape performance. The drug also showed an anxiolytic effect in the light/dark transition test as indicated by the increase in the time spent in the lighted compartment (control: 23.50 ± 2.45 s, muscimol: 47.30 ± 4.48 s). The present findings point to involvement of the BLA in the modulation of defensive responses that have been associated with GAD.

Functional MR Imaging of Psychogenic Amnesia: A Case Report

We present here a case in which functional MR imaging (fMRI) was done for a patient who developed retrograde psychogenic amnesia for a four year period of her life history after a severe stressful event. We performed the fMRI study for a face recognition task using stimulation with three kinds of face photographs: recognizable familiar faces, unrecognizable friends' faces due to the psychogenic amnesia, and unfamiliar control faces. Different activation patterns between the recognizable faces and unrecognizable faces were found in the limbic area, and especially in the amygdala and hippocampus.

role of adenosine A1 receptor activity of piriform cortex neurons on amygdala kindled seizures in rats

Considering the anticonvulsant effects of A1 Adenosine Receptors and the anatomical connections between piriform Cortex and Amygdala, in this study, the role of A1 adenosine receptors activity of piriform cortex neurons on amygdala kindled seizures was investigated in rats. The rats were fully kindled by daily electrical stimulation of amygdala. N6-cyclohexyleadenosine [CHA; 1,10 and 100 mM], as a selective A1 agonist and 1,3-dimethyl-8-cyclohexylexantine [CPT; 20 and 10 mM], as a selective A1 antagonist were microinjected [0.5ml, 0.25 ml/min] into the piriform cortex. Animals were stimulated at 5, 15 or 90 min after drug microinjection and seizure parameters were measured. Intra-piriform CHA [10 or 100 mM] reduced afterdischarge duration and stage 5 seizure duration and prolonged stage 4 latency significantly. Pretreatment with CPT [10 mM] 5 min before CHA [100 mM] eliminated the effects of CHA. These observations suggest that A1 adenosine receptors activity in piriform cortex reduced the seizure severity and attenuated the distribution of seizure activity to other brain regions

Análise crítica dos sistemas neurais envolvidos nas respostas de medo inato / Critical analysis of the neural systems organizing innate fear responses

O nosso entendimento das bases neurofisiológicas da reaçäo emocional do medo baseia-se em grande parte nos estudos que envolvem respostas condicionadas a estímulos fisicamente aversivos, como, por exemplo, o choque elétrico nas patas. Enquanto este paradigma parece ser útil para avaliarmos os sistemas neurais envolvidos na resposta do, assim chamado, medo condicionado (que tipicamente tem se limitado à observaçäo da resposta de congelamento), este paradigma parece ter sérias limitaçöes para investigarmos as bases neurais das respostas de medo em circunstancias naturais. Trabalhos recentes utilizando técnicas de lesöes neurais bem como de mapeamento funcional em animais expostos a predadores naturais, ou somente ao odor destes predadores, revelam uma série de estruturas neurais como responsáveis pelas respostas de medo inato, bastante distintas daquelas previamente implicadas nas respostas de condicionamento aversivo. Como revisto no presente trabalho, entre estas estruturas temos distritos diferenciados da zona medial do hipotálamo; setores específicos da amídala e do sistema septo-hipocampal, envolvidos, respectivamente no processamento de pistas relacionadas à presença do predador e na análise contextual do ambiente; e setores da matéria cinzenta periaquedutal, já classicamente envolvidos na expressäo de respostas de defesa. Estas informaçöes podem ser potencialmente importantes para a análise e terapêutica de psicopatologias relacionadas aos distúrbios da reaçäo emocional de medo

Organizaçäo neural de diferentes tipos de medo e suas implicaçöes na ansiedade / Neural organization of different types of fear: implications for the understanding of anxiety

A natureza das respostas de medo em animais expostos a situaçöes ameaçadoras depende da intensidade e da distância do estímulo aversivo. Esses estímulos podem ser potencialmente perigosos, distais ou proximais ao animal. Esforços têm sido feitos no sentido de identificar os circuitos neurais recrutados na organizaçäo das reaçöes defensivas a estas condiçöes aversivas. Neste artigo, sumarizamos evidências que associam os sistemas cerebrais de defesa ao conceito de medo-stress-ansiedade. Respostas de orientaçäo ao estímulo de perigo, à esquiva e à preparaçäo para o enfrentamento do perigo parecem estar associados à ansiedade. O giro do cíngulo e o córtex pré-frontal de um lado; o núcleo mediano da rafe, septo e o hipocampo de outro fazem parte dos circuitos cerebrais que integram essas respostas emocionais. No outro extremo, estímulos de medo que induzem formas ativas de defesa, mas pouco elaboradas, determinam estados emocionais de natureza diferente e parecem associadas a manifestaçöes elementares de medo. A substância cinzenta periaquedutal dorsal constitui o principal substrato neural para a integraçäo desses estados aversivos no cérebro. Comportamentos defensivos desse tipo säo produzidos pela estimulaçäo elétrica e química desta estrutura. A medida que os estímulos ameaçadores, potenciais e distais däo lugar a estímulos de perigo muito intensos ou säo substituídos por estímulos proximais de medo, ocorre uma comutaçäo (switch) dos circuitos neurais usualmente responsáveis pela produçäo de respostas condicionadas de medo para reaçöes defensivas com baixo nível de regulaçäo e organizaçäo que se assemelham aos ataques de pânico. Portanto, dependendo da natureza do evento estressor ou do estímulo incondicionado, o padräo de respostas defensivas orientadas e organizadas cede lugar a respostas motoras incoordenadas e incompletas. A amígdala e o hipotálamo medial podem funcionar como uma espécie de interface comutando os estímulos para os substratos neurais apropriados para elaboraçäo das respostas defensivas condicionadas ou incondicionadas

Hippocampal hyperexcitability facilitates amygdala kindling in rats.

BACKGROUND & OBJECTIVES: The amygdala and hippocampus are recognized as the two important structures in the brain involved in the development and control of kindled seizures. The study on the precise interconnection between these two regions can provide important insights into the functional anatomy of complex partial seizures. In this study the effect of an experimentally increased excitability in hippocampal neurons, via hippocampal kindling, on the amygdala kindling rate was investigated in rats. METHODS: Animals were divided into four groups. Tripolar electrodes were implanted in the amygdala and CA1 region of the dorsal hippocampus of animals of Groups 1, 3 and 4. In Group 2 animals, tripolar electrodes were only implanted in the amygdala. In Group 1, one week after surgery, the rats were kindled first from the hippocampus and the next day kindled by amygdala stimulation. In Groups 2 and 3, one week after surgery, rats were kindled from the amygdala. Group 4 animals had a recovery period of one week plus 32 days, which was the mean of the hippocampal kindling rate in Group 1, and then were kindled from the amygdala. RESULTS: In Group 1, the amygdala kindling rate (n; number of days for which animals were stimulated before a stage 5 motor convulsion is triggered) and seizure stage at day n/2 were significantly facilitated and increased respectively. There was also a significant positive correlation between hippocampal and amygdala kindling rates. INTERPRETATION & CONCLUSION: Results obtained show that an increase in hippocampal excitability can facilitate kindling from the amygdala. Thus, it is suggested that the hippocampus has an important role in the development and propagation of seizures from the amygdala.