Showing papers by "Trevor W. Robbins published in 1990"

The case for frontostriatal dysfunction in schizophrenia

Abstract: A frontostriatal hypothesis of schizophrenia is advanced which takes into account evidence from studies of neurochemical pathology, functional imaging, cognitive neuropsychology, and experimental and clinical psychopharmacology, in addition to factor analyses of the symptomatic heterogeneity of this disorder. This evidence is illuminated by the recent characterization of anatomically segregated, functionally distinct coiticostriatal loops which provide possible substrates for understanding the significance of functional changes in striatal and cortical dopaminergic activity interacting with other forms of structural pathology in schizophrenia.

Increased sensitivity to amphetamine and reward-related stimuli following social isolation in rats: possible disruption of dopamine-dependent mechanisms of the nucleus accumbens.

Abstract: These experiments compared isolation-reared and socially-reared rats in two complementary paradigms for measuring responding to signals of reward, both undrugged and following either systemic or intraaccumbensd-amphetamine (AMPH) In experiment 1, locomotor activity conditioned to food presentation was measured in rats exposed to a restricted feeding schedule The interaction between this conditioned activity, AMPH administration (05, 20, 35, 50 mg/kg IP) and motivational state was measured In experiment 2, hungry rats were trained to associate a compound light/noise stimulus with sucrose reward and were then implanted with guide cannulae in the nucleus accumbens In the test phase, responding on one of two novel levers produced the compound stimulus (conditioned reinforcer; CR) Responses on the other lever had no effect Each rat received four counterbalanced intra-accumbens infusions of AMPH (0, 3, 10, 20 µg) In both experiments, isolated rats responded more with stimuli associated with reward and this differential rearing effect was further exaggerated by AMPH The isolation-induced sensitivity to these stimuli and to AMPH was critically dependent on motivational variables Thus, in experiment 1 there were no differences between the groups when sated or during extinction and in experiment 2 the increased responding was restricted to the lever providing CR Measurements of the locomotor response to intra-accumbens AMPH (0, 3, 10 µg) also revealed that isolated rats were more sensitive to a low dose of the drug when tested food-deprived in a relatively novel environment These results suggest that the experience of isolation-rearing interacts either directly or indirectly with dopamine-dependent mechanisms of the nucleus accumbens to enhance the effects of reward-related stimuli

The role of the striatum in the mental chronometry of action: a theoretical review.

Abstract: Three converging fields are critically reviewed in the context of the functions of the striatum; its anatomical relationships; reaction time and motor programming studies of Parkinson's disease; and neuropsychological studies of the role of the striatum in similar functions in experimental animals. Special consideration is given to the possible existence of parallel, segregated cortico-striatal loops, the role of the mesencephalic dopamine innervation of the neostriatum, the utility of reaction time tasks for the separation of distinct \"routes for action\" and the development of analogous tests in animals with discrete and specific lesions of the striatum. Several elementary processes are identified that Reprint address: T.W. Robbins Department of Experimental Psychology, University of Cambridge, Cambridge, CB2 3EB, United Kingdom •Present address: Lab. Sensorimotor Research, National Eye Institute, N.I.H. Building 10, Rm 10C101, Bethesda, MD 20892, U.S.A. contribute to the early stages of response selection. These can be denoted as spatial, temporal and cognitive aspects of response set. The implications for striatal function and dysfunction, specifically in Parkinson's disease, are considered.

Enhanced behavioral conditioning to context and impaired behavioral and neuroendocrine responses to conditioned stimuli following ceruleocortical noradrenergic lesions: support for an attentional hypothesis of central noradrenergic function.

Abstract: This study tested the hypothesis that cortical noradrenaline (NA) depletion induced by 6-hydroxydopamine (6-OHDA) widens attentional span, impairing the acquisition of conditioning to an explicit stimulus while enhancing conditioning to contextual stimuli. Sham-operated and NA-depleted rats were exposed to pairings of an auditory (clicker) CS and (footshock) US in a distinctive environment. Half of the lesioned and half of the control animals were trained with a short trace interval between presentations of clicker and shock, and half with a long trace. Associative learning theory predicts that a long trace interval should bias intact animals towards stronger contextual conditioning and, in contrast, a short trace interval should bias controls towards stronger CS conditioning. During testing, NA-depleted animals showed impaired fear conditioning to explicit cues, compared with controls, indicated by their reduced suppression of drinking when the CS was introduced into a separate, lick-operant chamber. In contrast, the same animals exhibited enhanced fear of contextual cues, as shown by their greater preference for a “safe” environment over the one in which they were shocked. The behavioral and plasma corticosterone responses of individual animals to the CS were positively correlated in both the lesion and sham groups. Corticosterone levels corroborated the impairment in CS conditioning caused by the lesion. In contrast, behavioral and corticosterone responses to contextual stimuli were not significantly correlated in either group, and there was no enhancement of the corticosterone response to contextual stimuli in the lesioned animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Cortical, hippocampal, and striatal mediation of schedule-induced behaviors.

Abstract: The sequential occurrence of licking, locomotor activity, entries into the food magazine (panel pressing), and nonreenforced lever pressing engendered by a periodic schedule of food presentation were measured in each 60-s interreenforcement interval in normal and brain-damaged rats. The development of these responses was measured over 20 days in different groups of food-deprived rats that had received aspirations of the hippocampus, small lesions of the cortex overlying the hippocampus (hippocampal-operated control group), decortication, or 6-hydroxy-dopamine lesions of the caudate nucleus or nucleus accumbens. All lesions produced distinctive patterns of change in the measured behaviors, and dissociations as well as similarities in their effects were evident. These results are discussed with respect to dissociations in the motor and motivational effects of the various lesions and in terms of contemporary hypotheses of schedule-induced behavior.

Physiological correlates of schedule-induced activities in rats.

Abstract: Oxygen consumption and heart rate as well as a range of behavior variables were tracked continuously as rats adapted to a schedule of food delivery. Over 15 days of observation a majority of the subjects developed characteristic patterns of schedule-induced polydipsia (SIP) in which bouts of drinking reliably followed food delivery. Variations in food tray entries, oxygen consumption, heart rate, and, in the final stage of the experiment, rates of general activity were also time locked to food delivery in both rats exhibiting SIP and nondrinkers. However, the patterns of variation in these measures differed consistently between these two groups. Oxygen consumption varied over a wider range and reached higher levels in drinkers than nondrinkers. Additionally, heart rate was lower in the drinkers, which, in the final stage of the experiment, also exhibited depressed rates of food tray entries and general activity relative to the nondrinkers. Each of these between-subject differences was paralleled by differences within the drinking group between trials on which drinking occurred and trials on which it did not occur. The implications of these results on the utility of unidimensional energetic constructs are discussed.

In vivo neurochemical techniques in the analysis of behaviour.

Abstract: The chairman, T. W. Robbins (Cambridge) introduced this symposium on the use of in vivo neurochemical techniques with the observation that, although they had been introduced over a decade earlier, much of the discussion about them is still centred on the technical problems they pose, rather than how they can be used in the analysis of the neurochemical substrates of behaviour. C. Marsden (Nottingham) surveyed the pros and cons of the two techniques before going on to review recent findings on the neurochemical and behavioural effects of social isolation in the rat. He pointed out that voltammetry is fast but uncertain in specificity, whereas dialysis is the opposite. For these reasons, dialysis is best used to analyse the neurochemical ’states’ or ’traits’,