Extent of food restriction affects probability but not delay-based decision-making

Rodent studies on decision-making often use food rewards and food-restrict subjects in order to motivate performance. However, food restriction has widespread effects on brain and behavior, which depend on factors including extent of restriction and feeding schedule. These factors are well recognized for their effects on motivation, but may also cause effects on decision-making independent of motivation. We examined how the degree of weight-based food restriction in rats influenced decision-making on the probability and delay discounting tasks. Additionally, we examined how the method of food restriction (consistent amount vs. time constrained feeding schedule) influenced decision-making. Our results showed that the degree of weight-based food restriction significantly altered probability, but not delay discounting, and that these effects were not entirely explainable by differences in motivation. Additionally, the method of food restriction did not significantly influence discounting when animals were within the same range of weight-based restriction. Together, our findings suggest that the degree of food restriction may modulate the neural circuitry responsible for selective aspects of decision-making related to probability. Further, these data support the need for tight control and reporting of weight and feeding in studies relying on food restriction, and suggest that the effects of food restriction may be broader than previously considered.     

西方历史编纂的形而上学

历史不是一种时间,而是多种时间,彼此交错并彼此包含.因此,应该用多元时间观替代旧的时间观.--福柯(<读与写>第2卷,第279页)     

L-type voltage-gated calcium channels in conditioned fear: a genetic and pharmacological analysis

Using pharmacological approaches, others have suggested that L-type voltage-gated calcium channels (L-VGCCs) mediate both consolidation and extinction of conditioned fear. In the absence of L-VGCC isoform-specific antagonists, we have begun to investigate the subtype-specific role of LVGCCs in consolidation and extinction of conditioned fear using a molecular genetics approach. Previously, we used this approach to demonstrate that the Ca(v)1.3 isoform mediates consolidation, but not extinction, of contextually conditioned fear. Here, we used mice in which the gene for the L-VGCC pore-forming subunit Ca(v)1.2 was conditionally deleted in forebrain excitatory neurons (Ca(v)1.2(cKO) mice) to address the role of Ca(v)1.2 in consolidation and extinction of conditioned fear. We demonstrate that Ca(v)1.2(cKO) mice consolidate and extinguish conditioned fear as well as control littermates. These data suggest that Ca(v)1.2 is not critical for these processes and together with our previous data argue against a role for either of the brain-expressed L-VGCCs (Ca(v)1.2 or Ca(v)1.3) in extinction of conditioned fear. Additionally, we present data demonstrating that the L-VGCC antagonist nifedipine, which has been used in previous conditioned fear extinction studies, impairs locomotion, and induces an aversive state. We further demonstrate that this aversive state can enter into associations with conditioned stimuli that are present at the time that it is experienced, suggesting that previous studies using nifedipine were likely confounded by drug toxicity. Taken together, our genetic and pharmacological data argue against a role for Ca(v)1.2 in consolidation of conditioned fear as well as a role for L-VGCCs in extinction of conditioned fear.     

Conditional forebrain deletion of the L-type calcium channel Ca V 1.2 disrupts remote spatial memories in mice

To determine whether L-type voltage-gated calcium channels (L-VGCCs) are required for remote memory consolidation, we generated conditional knockout mice in which the L-VGCC isoform Ca(V)1.2 was postnatally deleted in the hippocampus and cortex. In the Morris water maze, both Ca(V)1.2 conditional knockout mice (Ca(V)1.2(cKO)) and control littermates displayed a marked decrease in escape latencies and performed equally well on probe trials administered during training. In distinct contrast to their performance during training, Ca(V)1.2(cKO) mice exhibited significant impairments in spatial memory when examined 30 d after training, suggesting that Ca(V)1.2 plays a critical role in consolidation of remote spatial memories.     

So many options,so little time: The roles of association and competition in underdetermined responding

How do we make decisions when faced with multiple options? In the domain of language, some evidence suggests that we exert cognitive control in order to respond in such underdetermined situations when a good option is hard to find but not when we must select among competing options. However, this conclusion, and conclusions about the neural substrates supporting underdetermined responding, are made on the basis of measures that confound retrieval and selection demands. The present study introduces measures based on latent semantic analyses that better capture the underlying theoretical constructs of association strength and competition. These measures revealed independent effects of retrieval and selection demands on reaction times in verb generation and sentence completion tasks. These results challenge existing accounts of underdetermined responding and highlight the need for unconfounded measures of association strength and competition in studies of localization. We propose a new model governed by both absolute and relative activation levels of alternative responses. 2008 Psychonomic Society, Inc. Author Note     

Affective primes suppress attention bias to threat in socially anxious individuals

Anxious individuals show an attention bias towards threatening information. However, under conditions of sustained environmental threat this otherwise-present attention bias disappears. It remains unclear whether this suppression of attention bias can be caused by a transient activation of the fear system. In the present experiment, high socially anxious and low socially anxious individuals (HSA group, n=12; LSA group, n=12) performed a modified dot-probe task in which they were shown either a neutral or socially threatening prime word prior to each trial. EEG was collected and ERP components to the prime and faces displays were computed. HSA individuals showed an attention bias to threat after a neutral prime, but no attention bias after a threatening prime, demonstrating that suppression of attention bias can occur after a transient activation of the fear system. LSA individuals showed an opposite pattern: no evidence of a bias to threat with neutral primes but induction of an attention bias to threat following threatening primes. ERP results suggested differential processing of the prime and faces displays by HSA and LSA individuals. However, no group by prime interaction was found for any of ERP components.