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In 1954, when Olds and Milner discovered rewarding areas in the rat brain, it seemed as if the drive reductionists would have to revise their basic theory. Until that time the dogma was that an action would be reinforced if it led to a reduction in drive or drive stimuli. The idea that an increase in stimulation could be rewarding was contrary to the most widely accepted theories, and, in fact, the affect of an increase in stimulation was commonly regarded as punishing. [...]

Several investigations suggest that the amygdala plays a significant role in behavioral inhibition. Brutkowski, Fonberg and Mempel (1960) reported that bilateral lesions of the amygdaloid complex in dogs severely impaired inhibitory conditioned responses, while excitatory conditioned responses remained unaffected. Bilateral lesions of the amygdala have also been shown to impair the acquisition of the conditioned emotional response (Kellicutt & Schwartzbaum, 1963), and the retention of an auditory frequency discrimination in a bar pressing situation for food (Schwartzbaum, Thompson & Kellicutt, 1964). In the latter study, amygdaloid lesioned rats typically persisted in responses that were no longer adaptive, that is, they increased responding under nonreinforced conditions. [...]

Experiments utilizing techniques of ablation, as well as electrical and chemical stimulation, have all implicated the lateral hypothalamus as an area of central importance in the regulation of food intake. Anand and Brobeck (1951) were the first to demonstrate that bilateral lesions placed lateral to the ventromedial hypothalamic nucleus in both rats and cats were consistently associated with the development of a temporary or permanent aphagia (refusal to eat). This finding has been duplicated in various other animal species including birds (Andersson, Fabricus, Svensson & Akerman, 1960: Feldman, Larsson, Dimick, & Leprovsky, 1957) and monkeys (Anand, Dua & Shoenberg, 1955). [...]

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Distinct brain regions process innocuous vibration and cutaneous heat pain. The role of these areas in the perception of pain is still a matter of debate; and the role of these areas in the mediation of memory of somatosensory stimuli is uncertain and has not been studied with brain imaging in healthy human volunteers. All experiments described here, involved an experimental design, which included a delayed-discrimination paradigm and functional magnetic resonance imaging (fMRI). In manuscript #1, we aimed at unraveling the cerebral correlates of attention and spatial localization of innocuous vibrotactile stimuli applied to the right volar surface of the forearm. In this study, we report that increased degrees of attention to the vibrotactile stimuli were associated with heightened levels of activation in several brain areas. In manuscript #2, we investigated the short-term memory for sensory aspects (intensity and location) of cutaneous heat pain delivered to two areas (thenar and hypothenar eminences) of the palm of the right hand. In this experiment, the memory and control trials were presented in blocks, whereby the subjects could predict what trials were going to follow. This study revealed that the presentation of painful stimuli evoked activation in different brain regions than those activated during the online maintenance (interstimulus interval or ISI) of the intensity and spatial features of those stimuli; a process, which I will refer to short-term memory. In manuscript #3, we investigated again short-term memory for sensory aspects of heat pain (as in manuscript #2), but in this case, the memory and control trials were presented in a randomized order. In this study, we found that the perception and short-term memory of pain were processed by a comparable network of areas. The predictability of the memory and control trials may have contributed to these findings. / La vibration inoffensive ainsi que la chaleur douloureuse cutanée sont traitées pardifférentes régions du cerveau. Le rôle de ces régions dans la perception de la douleurest controversé; et le rôle de ces régions dans la mémoire des stimuli somatosensorielsest incertain et n'a jamais encore été étudié en imagerie cérébrale chez des sujetshumains sains. Le design expérimental de toutes les études décrites ici comprenait unparadigme de 'delayed-discrimination' et l'imagerie par résonance magnétiquefonctionnelle (IRMf). L'étude #1 visait à élucider les corrélats cérébraux de l'attention etde la localisation spatiale des stimuli vibrotactiles inoffensifs présentés à la faceantérieure de l'avant-bras droit. Dans cette étude, nous avons trouvé que des degrésélevés d'attention portée aux stimuli vibrotactiles étaient associés à des niveaux accrusd'activation dans plusieurs zones du cerveau. Dans l'étude #2, nous avons enquêté surla mémoire à court-terme des caractéristiques sensorielles (intensité et emplacement)de la chaleur douloureuse cutanée présentée à deux endroits (éminences thénar ethypothénar) de la paume de la main droite. Dans cette étude, les essais mémoire etcontrôle étaient présentés en bloc, ou de sorte que les participants pouvaient prévoir dequel type serait le prochain essai. Cette étude a révélé que la présentation des stimulidouloureux a évoqué une activation de différentes régions cérébrales que celles quiétaient activées lors de la rétention de l'intensité et de l'emplacement des stimulationsdurant l'intervalle inter-stimuli (liS); un processus que je qualifierai de mémoire à courtterme.Dans l'étude #3, nous avons également enquêté sur la 'mémoire à court-termedes aspects sensoriels de la chaleur douloureuse (tout comme dans l'étude #2), maisdans ce cas, les essais mémoire et contrôle étaient présentés de façon aléatoire. Danscette étude, nous avons trouvé que la perception de la douleur ainsi que la mémoire àcourt-terme de la douleur étaient traitées par un réseau de régions semblable. Laprévisibilité des essais mémoire et contrôle peut avoir contribué à ce résultat.