Stimulation site determines the conditioned effects of kindling in rats: anterior neocortex versus amygdala

Rats received 53 stimulations to either the left basolateral amygdala (BA) or left anterior neocortex (AN) in one environment (CS+) and 53 sham stimulations (the stimulation lead was attached but no current was delivered) in another environment (CS-), quasirandomly over 54 days. Confirming a previous report [Barnes, S.J., Pinel, J.P., Francis, L.H. & Wig, G.S. (2001) Behav. Neurosci., 115, 1065-1072], as BA kindling progressed, the CS+ began to elicit more defensive behaviours (i.e. less activity, more freezing and avoidance of the CS+) than the CS-, and at the end of the experiment, convulsions elicited in the CS+ were more severe than those elicited in the CS-. Like BA kindling, AN kindling led to less activity in the CS+; but unlike BA kindling, AN kindling led to more wet-dog-shakes and less, rather than more, severe convulsions in the CS+. During AN kindling, the mean number of wet-dog-shakes in the CS+ was negatively correlated with the mean convulsion class, suggesting that wet-dog-shakes contribute to the inherent variability of AN kindling. These findings confirm that inherent conditioned effects influence kindled convulsions and interictal behaviour and establish for the first time that the pattern of these conditioned effects is a function of the kindling site.     

Dopamine and noradrenaline efflux in the rat prefrontal cortex after classical aversive conditioning to an auditory cue

We used bilateral microdialysis in the medial prefrontal cortex (PFC) of awake, freely moving rats to study aversive conditioning to an auditory cue in the controlled environment of the Skinner box. The presentation of the explicit conditioned stimuli (CS), previously associated with foot shocks, caused increased dopamine (DA) and noradrenaline (NA) efflux. This conditioned response was dependent on the immediate pairing of the two stimuli; in the pseudoconditioned group that received an equal number of both stimuli, but in an unpaired fashion, no conditioned increases in efflux were observed.     

State-dependent effects of alcohol on explicit memory: the role of semantic associations

Rationale: Memory performance can be facilitated when the context in which retrieval occurs matches the context in which learning initially took place in two separate ways, in form of interactive or independent context. In the present study, the differential effects of alcohol, as independent context, on the free recall of items of high or low semantic associations were investigated. The high and low associations offer different strengths of interactive context at stimulus input, i.e. context that influences what will be stored. Methods: Using a state-dependent retrieval paradigm, alcohol (0.8 g/kg) or placebo was administered prior to encoding and/or retrieval and their effects were tested using measures of free recall. Forty-eight participants were tested according to a traditional state-dependent retrieval design where half of the subjects studied the items under alcohol (A), half under placebo (P) followed by retrieval of the items under A or P giving four groups (AA, AP, PA, PP). Results: Delayed free recall was significantly impaired when alcohol was administered prior to both encoding and retrieval of study material (P<0.05). Alcohol administered prior to encoding and prior to retrieval decreased especially the recall of high association items (P<0.05). Participants in the same-state groups (AA, PP) recalled fewer low association items than participants in disparate state groups (AP, PA; P<0.05). This effect of drug state on low associations may reflect an inability of weaker cues to facilitate retrieval in the presence of stronger cues (i.e. high associations and drug). Indeed, participants in the same-state groups recalled a greater percentage of material in form of high association items than participants in disparate-state groups (P<0.05). Conclusions: These results demonstrate that alcohol given at encoding and at retrieval specifically impairs retrieval of high association items. However, if the drug state is the same at encoding and at retrieval, the items with the high associations represent a higher proportion of the total recalled items. These data suggest that alcohol may provide an internal context that can facilitate retrieval of information, acquired in semantic context, which otherwise would have been lost. Received: 22 September 1999 / Final version: 19 November 1999     

Childhood overweight: a contextual model and recommendations for future research

The prevalence of overweight among children has doubled within the past two decades. Increases in the rate of childhood overweight are of particular concern due to the negative health and psychological effects noted among overweight children. As shown by previous research, the development of childhood overweight involves a complex set of factors from multiple contexts that interact with each other to place a child at risk of overweight. This multifaceted system can be conceptualized using Ecological Systems Theory (EST). EST highlights the importance of considering the context(s), or ecological niche, in which a person is located in order to understand the emergence of a particular characteristic. In the case of a child, the ecological niche includes the family and the school, which are in turn embedded in larger social contexts including the community and society at large. In this review, EST is used as a framework with which to summarize research assessing predictors of childhood overweight. Specifically, child characteristics that place children at risk of the development of overweight (including dietary intake, physical activity, and sedentary behaviour) will be reviewed while taking into consideration the influence of the familial environment, the school environment, and the community and larger social environments. It is concluded that future research needs to adopt a broader contextual approach in order to understand and intervene against the processes leading to the development of overweight among children and that the use of theories or paradigms such as EST will facilitate developing and testing models of causal processes.     

Spatial attention and interhemispheric visuomotor integration in the absence of the corpus callosum

In the lateralized simple reaction time (SRT) task with unimanual responses (Poffenberger paradigm), reaction times (RTs) are faster with ipsilateral (uncrossed) than with contralateral (crossed) response hand-target hemifield combinations. The difference between crossed and uncrossed responses (CUD) has typically been interpreted to reflect callosal transfer time. Indeed, acallosal subjects and split-brain subjects have longer CUDs than control subjects. However, a few recent studies have demonstrated that, contrary to classical findings, the CUD is also affected by non-anatomical factors. Here we show that the CUD is also affected by non-anatomical factors in patients with agenesis of the corpus callosum and complete commissurotomy where interhemispheric transfer must be subcallosal. We tested acallosal subject M.M. and split brain patient A.A. on a lateralized SRT task with their arms alternately uncrossed (natural arms position) or crossed (unnatural arms position) across blocks of trials. The results revealed a significant effect of arms crossing on the size and direction of the CUD as previously found in normal subjects [Mooshagian, E., Iacoboni, M., & Zaidel, E. (2008). The role of task history in simple reaction time to lateralized light flashes. Neuropsychologia, 46(2), 659-664]. This suggests that non-anatomical factors that modulate interhemispheric visuomotor integration may occur in absence of the corpus callosum. Anterior commissure and interhemispheric cortico-subcortical pathways are likely implicated in these effects.     

Emotional dysregulation in dysphoria: Support for emotion context insensitivity in response to performance-based feedback

The Emotion Context Insensitivity (ECI) hypothesis predicts that individuals experiencing a sad mood will show diminished reactivity to emotionally evocative stimuli and will not differentiate emotional responses across contexts. Previous work has primarily been limited to studying depressed individuals' emotional responses to film clips, images, and autobiographical memories. The current study builds upon this work by examining emotional reactivity of dysphoric (n = 47) and non-dysphoric (n = 54) individuals to positive and negative feedback about their performance on a task they were led to believe measured social intelligence. Overall, dysphoric individuals reported higher negative emotion and lower positive emotion than non-dysphoric individuals before, during, and after feedback. However, consistent with ECI, dysphoric individuals displayed attenuated emotional reactivity to negative feedback compared to controls. Further, dysphoric individuals' emotional response did not differ to positive and negative feedback, whereas the non-dysphoric group appropriately differentiated their emotional response across these contexts. Findings support the ECI hypothesis and broaden its scope to include emotional reactivity to self-relevant performance feedback.     

Family Composition, Parental Involvement and Young Children's Academic Achievement

This study examined whether first-, second-, and third-grade students' achievement in language and mathematics was affected by factors from both the family context, including family size, number of adult caregivers, and parents' educational level, and the type of school related activities practised by parents. Participants in the study were 333 students (grades 1-3) whose parents had completed and returned a questionnaire designed to measure parents' attitude toward school and the extent of their involvement in school related activities. Academic achievement was related to measures of family composition (family size, number of adult caregivers, and parents' educational level). After controlling for race and gender, parents' educational level was associated with the students' scores on achievement tests. Furthermore, students whose parents engaged in learning activities at home were more likely to obtain higher achievement (language) scores. The study lends support to current practices commonly found in early childhood programs for involving parents in their children's schooling.     

Phasic vs Sustained Fear in Rats and Humans: Role of the Extended Amygdala in Fear vs Anxiety

Data will be reviewed using the acoustic startle reflex in rats and humans based on our attempts to operationally define fear vs anxiety. Although the symptoms of fear and anxiety are very similar, they also differ. Fear is a generally adaptive state of apprehension that begins rapidly and dissipates quickly once the threat is removed (phasic fear). Anxiety is elicited by less specific and less predictable threats, or by those that are physically or psychologically more distant. Thus, anxiety is a more long-lasting state of apprehension (sustained fear). Rodent studies suggest that phasic fear is mediated by the amygdala, which sends outputs to the hypothalamus and brainstem to produce symptoms of fear. Sustained fear is also mediated by the amygdala, which releases corticotropin-releasing factor, a stress hormone that acts on receptors in the bed nucleus of the stria terminalis (BNST), a part of the so-called ‘extended amygdala.'' The amygdala and BNST send outputs to the same hypothalamic and brainstem targets to produce phasic and sustained fear, respectively. In rats, sustained fear is more sensitive to anxiolytic drugs. In humans, symptoms of clinical anxiety are better detected in sustained rather than phasic fear paradigms.