Odor-specific habituation arises from interaction of afferent synaptic adaptation and intrinsic synaptic potentiation in olfactory cortex

Segmentation of target odorants from background odorants is a fundamental computational requirement for the olfactory system and is thought to be behaviorally mediated by olfactory habituation memory. Data from our laboratory have shown that odor-specific adaptation in piriform neurons, mediated at least partially by synaptic adaptation between the olfactory bulb outputs and piriform cortex pyramidal cells, is highly odor specific, while that observed at the synaptic level is specific only to certain odor features. Behavioral data show that odor habituation memory at short time constants corresponding to synaptic adaptation is also highly odor specific and is blocked by the same pharmacological agents as synaptic adaptation. Using previously developed computational models of the olfactory system we show here how synaptic adaptation and potentiation interact to create the observed specificity of response adaptation. The model analyzes the mechanisms underlying the odor specificity of habituation, the dependence on functioning cholinergic modulation, and makes predictions about connectivity to and within the piriform neural network. Predictions made by the model for the role of cholinergic modulation are supported by behavioral results.Filtering sensory input is critical for information processing tasks such as background segmentation, and shifting processing power away from redundant, stable, or repetitive stimuli toward dynamic, novel stimuli. A critical aspect of this filtering however, is stimulus specificity. Under most circumstances it may be most beneficial to selectively filter the redundant stimulus, while maintaining responsiveness to different, though perhaps highly similar stimuli.In the olfactory system, short-term habituation to stable or repeated odorants involves a metabotropic glutamate receptor (mGluR)-dependent depression of afferent synapses to the piriform cortex (Best and Wilson 2004). Blockade of group III mGluR receptors prevents cortical adaptation odors (Best and Wilson 2004), and reduces short-term habituation of odor-evoked reflexes (Best et al. 2005) and odor investigation (Yadon and Wilson 2005; Bell et al. 2008; McNamara et al. 2008). This short-term habituation is highly odor specific, with minimal cross-adaptation of piriform cortical single-unit responses or cross-habituation of behavioral responses to similar odors, including between mixtures and their components (Wilson 2000; Cleland et al. 2002). Interestingly, there is an experience-dependent component to short-term habituation odor specificity. The odor specificity is most pronounced for familiar odors, with very brief (<20 sec) exposure to odors producing more generalization, and longer exposures (>50 sec) sufficient to permit strong odor specificity in cortex adaptation (Wilson 2003).The homosynaptic nature of afferent synaptic depression underlying cortical adaptation (Wilson 1998; Best and Wilson 2004) may contribute to this odor specificity. However, the experience dependence suggests that there may be an additional process involved. In fact, theoretical views of piriform cortical function suggest that the cortex learns previous patterns of input via potentiation of intracortical association fiber synapses (Hasselmo et al. 1990; Barkai et al. 1994; Haberly 2001; Linster et al. 2003). This autoassociative process essentially creates a template of previous network activity, against which new input patterns can be compared, allowing enhanced discrimination between similar patterns, as well as completion of degraded patterns (Barkai et al. 1994; Barnes et al. 2008). In support of this hypothesis, previous work has demonstrated that disruption of normal synaptic potentiation in association fiber synapses through blockade of cholinergic muscarinic receptors (Patil et al. 1998; Linster et al. 2003), reduces odor specificity of cortical adaptation (Wilson 2001b), prevents the effects of odor experience on subsequent behavioral cross-habituation (Fletcher and Wilson 2002), and disrupts odor discrimination (Linster et al. 2001).The present series of studies further explored the role of combined afferent synaptic depression and intracortical association fiber synaptic potentiation on the specificity of cortical adaptation and odor habituation. Using a computational model of the olfactory system (Linster et al. 2007), the results suggest that activity-dependent association fiber plasticity is necessary to account for the specificity of odor habituation. Furthermore, in behavioral experiments blockade of cholinergic muscarinic receptors during habituation enhances generalization of odor habituation, consistent with the modeling and with previous electrophysiological results.     

Who gets a mentor? A longitudinal assessment of the rising star hypothesis

This study assessed the rising star hypothesis, which proposes that individuals who are on the fast track to career success are more likely to gain mentors than others. The study used a sample of employees who had never been mentored and examined the relationship between rising star attributes measured at Time 1 and the attainment of a mentor a year later. In support of the hypothesis, individuals who were on the fast-track for promotion, had higher advancement expectations, and engaged in more proactive career behaviors were more likely to gain a mentor than individuals lacking these attributes. Implications of these results for the theory, research and practice of mentoring are discussed.     

Competitive versus cooperative attitudes in crossed categorization effects: testing the category dominance and equivalence models

Participants' (N = 256) competitive or cooperative attitudes toward national groups were activated by their reading 1 of 2 selected newspaper articles. Participants then judged the competence and attractiveness of a stranger who was categorized, separately for race and nationality, as belonging to an out-group or in-group. As predicted, the activated competitive attitude produced responses prescribed by the model of category dominance by nationality. In the condition of cooperative attitudes, however, competence responses were consistent with the model of equivalence (i.e., no effect of category) and attraction responses were consistent with the model of category dominance by race. The authors discuss reasons for the discrepant models in the condition of cooperative attitudes and the implications of these findings.     

A man with multiple disabilities using a head‐turning response to reduce the effects of his drooling

A man with multiple disabilities was taught to perform a head‐turning response to activate optic sensors embedded in a small spongy structure at his shoulder and produce preferred stimuli. By touching the spongy structure with chin and mouth (i.e., to activate the sensors), the man would clean these areas thus curbing the effects of his drooling. Data showed that the man increased the frequency of his head‐turning responses and reduced drooling effects (chin wetness) through the intervention and a 3‐month follow‐up. Forty university students, who were involved in a social validation assessment, indicated that the intervention was suitable and enjoyable to the man, had a social/educational function, and represented an approach that they supported. Copyright © 2008 John Wiley & Sons, Ltd.     

Acting and Believing Under the Guise of Normative Reasons

In this paper, I defend an account of the reasons for which we act, believe, and so on for any Ф such that there can be reasons for which we Ф. Such reasons are standardly called motivating reasons. I argue that three dominant views of motivating reasons (psychologism, factualism and disjunctivism) all fail to capture the ordinary concept of a motivating reason. I show this by drawing out three constraints on what motivating reasons must be, and demonstrating how each view fails to satisfy at least one of these constraints. I then propose and defend my own account of motivating reasons, which I call the Guise of Normative Reasons Account. On the account I defend, motivating reasons are propositions. A proposition is the reason for which someone Ф‐s when (a) she represents that proposition as a normative reason to Ф, and (b) her representation explains, in the right way, her Ф‐ing. As I argue, the Guise of Normative Reasons Account satisfies all three constraints on what motivating reasons must be, and weathers several objections that might be leveled against propositionalist views.     

Revisiting Ego Depletion: Moderators and Measurement

We developed and validated two web-based tasks to induce and measure ego depletion in two online experiments (N?=?122 and N?=?788). Ego depletion describes the phenomenon that exerting self-control temporarily reduces people’s capacity to subsequently control themselves. To induce ego depletion, we adapted the e-crossing task, and to measure ego depletion, we adapted the color Stroop task. We successfully induced ego depletion. Participants’ implicit theories about willpower as well as their mood moderated ego depletion. We also discuss several methodological issues and compare different approaches of measuring ego depletion using aggregated reaction times.     

Bedroom design and decoration: gender differences in preference and activity

This investigation examined gender differences in niche-building preference and activity among 238 8th and 9th grade boys and girls. A questionnaire was developed to measure both the actual and preferred bedroom content, bedroom design activity, and the level of perceived influence by the immediate and extended family, friends, and social institutions. Gender differences were identified for preference, activity, and influence in bedroom design and decoration. Girls and boys differed in the type of items contained in their bedrooms. Girls' rooms contained stuffed animals and pictures of people, including themselves, more frequently than the boys' rooms. In contrast, boys' rooms contained sports-related items, and things for building or that they had built themselves. Although bedroom design activity for both boys and girls was influenced by older teens, friends, media, and popular culture, boys (but not girls) were also influenced by their mothers, fathers, girlfriends, and activities such as sports, Boy or Girl Scouts, and music lessons.