Representation is representation of similarities

Advanced perceptual systems are faced with the problem of securing a principled (ideally, veridical) relationship between the world and its internal representation. I propose a unified approach to visual representation, addressing the need for superordinate and basic-level categorization and for the identification of specific instances of familiar categories. According to the proposed theory, a shape is represented internally by the responses of a small number of tuned modules, each broadly selective for some reference shape, whose similarity to the stimulus it measures. This amounts to embedding the stimulus in a low-dimensional proximal shape space spanned by the outputs of the active modules. This shape space supports representations of distal shape similarities that are veridical as Shepard's (1968) second-order isomorphisms (i.e., correspondence between distal and proximal similarities among shapes, rather than between distal shapes and their proximal representations). Representation in terms of similarities to reference shapes supports processing (e.g., discrimination) of shapes that are radically different from the reference ones, without the need for the computationally problematic decomposition into parts required by other theories. Furthermore, a general expression for similarity between two stimuli, based on comparisons to reference shapes, can be used to derive models of perceived similarity ranging from continuous, symmetric, and hierarchical ones, as in multidimensional scaling (Shepard 1980), to discrete and nonhierarchical ones, as in the general contrast models (Shepard & Arabie 1979; Tversky 1977).     

Grasp posture planning during multi-segment object manipulation tasks — Interaction between cognitive and biomechanical factors

The present study examined adaptations in the planning of initial grasp postures during a multi-segment object manipulation task. Participants performed a grasping and placing task that consisted of one, two, or three movement segments. The position of the targets was manipulated such that the degree of object rotation between the home and temporally proximal positions, and between the temporally proximal and distal target positions, varied. Participants selected initial grasp postures based on the specific requirements of the temporally proximal and temporally distal action segments, and adjustments in initial grasp posture depended on the temporal order of target location. In addition, during the initial stages of the experimental session initial grasp postures were influenced to a larger extent by the demands of the temporally proximal segment. However, over time, participants overcame these cognitive limitations and adjusted their initial grasp postures more strongly to the requirements of the temporally distal segment. Taken together, these results indicate that grasp posture planning is influenced by cognitive and biomechanical factors, and that participants learn to anticipate the task demands of temporally distal task demands, which we hypothesize, reduce the burden on the central nervous system.     

Support for context effects on segmentation and segments depends on the context

Listeners must adapt to differences in speech rate across talkers and situations. Speech rate adaptation effects are strong for adjacent syllables (i.e., proximal syllables). For studies that have assessed adaptation effects on speech rate information more than one syllable removed from a point of ambiguity in speech (i.e., distal syllables), the difference in strength between different types of ambiguity is stark. Studies of word segmentation have shown large shifts in perception as a result of distal rate manipulations, while studies of segmental perception have shown only weak, or even nonexistent, effects. However, no study has standardized methods and materials to study context effects for both types of ambiguity simultaneously. Here, a set of sentences was created that differed as minimally as possible except for whether the sentences were ambiguous to the voicing of a consonant or ambiguous to the location of a word boundary. The sentences were then rate-modified to slow down the distal context speech rate to various extents, dependent on three different definitions of distal context that were adapted from previous experiments, along with a manipulation of proximal context to assess whether proximal effects were comparable across ambiguity types. The results indicate that the definition of distal influenced the extent of distal rate effects strongly for both segments and segmentation. They also establish the presence of distal rate effects on word-final segments for the first time. These results were replicated, with some caveats regarding the perception of individual segments, in an Internet-based sample recruited from Mechanical Turk.     

Dopamine induces LTP differentially in apical and basal dendrites through BDNF and voltage-dependent calcium channels

The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC). Activation via NMDAR is critical for the induction of DA-LTP in both apical and basal dendrites, but only BDNF is required for the induction and maintenance of DA-LTP in apical dendrites. We report that dopaminergic modulation of LTP is lamina-specific at the Schaffer collateral/commissural synapses in the CA1 region.     

The distance effect and level of expertise: Is the optimal external focus different for low-skilled and high-skilled performers?

Focusing attention on a movement effect that is farther away from the body (distal external focus) has been shown to result in more effective motor performance or learning than focusing on an effect that is in greater proximity to the body (proximal focus). The present study examined whether the distance of the external focus impacts the performance of relatively inexperienced and experienced performers differently. Low-skilled and high-skilled volleyball players passed a volleyball continuously to a target. In the proximal focus condition they were asked to concentrate on the “platform,” whereas in the distal focus condition they were instructed to concentrate on the target. The high-skilled group's accuracy scores were higher in the distal relative to proximal focus condition. However, low-skilled players' accuracy scores was greater in the proximal relative to distal focus condition. We argue that the optimal distance of the external focus depends on the level of expertise when the skill requires a specific movement technique. An external focus on that technique seems to be more advantageous for low-skilled performers. In contrast, when the movement pattern has become more automatic (high-skilled performers), a focus on the overall movement effect is more beneficial.     

Family predictors of antisocial behavior in adolescence

The goal of the present study was to examine the combined and unique ability of different aspects of family functioning to predict involvement in antisocial behavior in a large nonclinical (community) sample of adolescents. Distinction was made between global (e.g., family socioeconomic status), distal (dispositional characteristics of parents), contextual (family characteristics), and proximal (parent-child interaction) factors that operate within families. Results show that proximal factors were significant predictors of antisocial behavior, independent of their shared variance with other factors. Consistent with the hypothesized mediational model, the effects of distal and contextual factors appear to be mostly indirect: after their association with proximal factors was taken into account, these factors were no longer significantly related to antisocial behavior. The implications of these findings for planning of developmentally appropriate interventions for adolescents and their families are discussed.     

Apical dendrite activity in cognition and consciousness

The ongoing steady nature of consciousness in everyday life implies that the underlying neural activity possesses a high level of stability. The prolonged cognitive events of sustained attention, imagery, and working memory also imply high stability of underlying neural activity. This paper proposes that stabilization of neural activity is produced by apical dendrite activity in pyramidal neurons within recurrent corticothalamic circuits, and proposes that the wave activities of apical dendrites that stabilize ongoing activity constitute the subjective impressions of an attended object and the entire sensory background. The cortical minicolumn, as the functional unit of the cortex, is separated into an axis consisting of layer 5 pyramidal neurons and a surrounding shell consisting of layer 2/3 pyramidal neurons. It is proposed that apical dendrites of the axis generate sensory impressions, and basal dendrites of the shell process the brief-lasting input-output identifications of objects that give rise to ideas.     

Potentiation and overshadowing in odor-aversion learning: Role of method of odor presentation,the distal-proximal cue distinction,and the conditionability of odor

Four experiments with rat subjects examined interactions between odors and tastes in compound aversion conditioning. In Experiments 1 and 2, a saccharin taste potentiated the conditioning of an almond odorant presented on a cup near the location of the drinking spout, but overshadowed the same odorant when it was mixed in drinking water. This difference depended on the type of odor administered during conditioning rather than testing (Experiment 2). Experiments 3 and 4 examined implications of two other differences between the cup and drink odors: (1) while the cup odor was a distal cue that suppressed approach to the spout, the drink odor was primarily a proximal cue that suppressed consumption, and (2) the cup odor was less conditionable than the drink odor when the stimuli were conditioned alone. In Experiment 3, unlike the proximal saccharin taste, the proximal drink odor failed to potentiate the conditioning of a different distal odor. In Experiment 4, substantial dilution of the proximal drink's concentration resulted in both weaker conditioning of the stimulus alone, and potentiation of its conditioning by saccharin. The results suggest that the difference in the conditionability of the cup and drink odors, and not their status as distal and proximal cues, may be critical in the production of potentiation. Weakly conditionable target stimuli are uniquely potentiated by saccharin.     

Do object-category selective regions in the ventral visual stream represent perceived distance information?

It is well established that scenes and objects elicit a highly selective response in specific brain regions in the ventral visual cortex. An inherent difference between these categories that has not been explored yet is their perceived distance from the observer (i.e. scenes are distal whereas objects are proximal). The current study aimed to test the extent to which scene and object selective areas are sensitive to perceived distance information independently from their category-selectivity and retinotopic location. We conducted two studies that used a distance illusion (i.e., the Ponzo lines) and showed that scene regions (the parahippocampal place area, PPA, and transverse occipital sulcus, TOS) are biased toward perceived distal stimuli, whereas the lateral occipital (LO) object region is biased toward perceived proximal stimuli. These results suggest that the ventral visual cortex plays a role in representing distance information, extending recent findings on the sensitivity of these regions to location information. More broadly, our findings imply that distance information is inherent to object recognition.     

Effects of walking on various inclines on EMG patterns of lower limb muscles in humans

Myoelectric signals from several muscles of the lower limb were studied during treadmill locomotion over various inclines. A pattern recognition technique was used to analyse these activity patterns. The analyses revealed the following rules. These are common features among the various muscle activity patterns. The results suggest that the limb is controlled as a unit. Both phasic and average components of the muscle activity patterns are modulated to meet demands imposed by the various inclines. The distal muscles in general are more tightly controlled than the proximal muscles. The changes in average EMG values are muscle-specific, and are not similar for the stance and swing phases of the step cycle. On average, the proximal muscles show greater increases than the distal muscles. These results are compared with those found previously in the different speed and stride-length condition. Studies such as these shed light on the adaptability of the basic locomotor synergy.     

TEST OF A MULTISTAGE MODEL OF DISTAL AND PROXIMAL ANTECEDENTS OF LEADER PERFORMANCE

The authors developed and tested a multistage model of distal and proximal predictors of leader performance in an effort to shed greater light on the intermediate linkages between broad leader traits and performance. Predictor and criterion data were obtained from 471 noncommissioned officers in the U.S. Army. A model with cognitive ability and 3 of the Big 5 personality factors as distal antecedents, leadership experiences and motivation to lead as semidistal antecedents, and the knowledge, skills, and ability (KSAs) to lead as proximal antecedents of leader performance provided a good fit to the data. More specifically, the effects of the distal and semidistal antecedents on leader performance were partially mediated by more proximal variables, whereas leader KSAs demonstrated a relatively strong, direct influence on performance. The 1 exception was that Conscientiousness—a hypothesized distal antecedent—had a notable direct effect on leader performance. The implications of these findings for leadership research and practice are discussed.     

Tactile pattern discrimination at adjacent locations along the proximal-distal axis of the index finger

A discrimination task was used to examine how locations on the glabrous skin of the terminal and middle phalanges of the index finger affect the perceived shape of tactile patterns. On each trial, a pair of same-shape or different-shape patterns was presented successively on the distal half, on the proximal half, or on both halves of a phalanx. Observers responded "same" or "different" depending on the perceived pattern shape. Performance was compared between the two phalanges, with two different pattern sets. For patterns at separate locations, performance was uniformly poor. For patterns at the same location, performance was better on the distal halves than on the proximal halves of both phalanges for one pattern set but not for the other. Performance was best on the distal half of the terminal phalanx. The results are discussed in terms of the densities of innervation of first-order afferents.     

Disaggregating the Distal,Proximal, and Time-Varying Effects of Parent Alcoholism on Children’s Internalizing Symptoms

We tested whether children show greater internalizing symptoms when their parents are actively abusing alcohol. In an integrative data analysis, we combined observations over ages 2 through 17 from two longitudinal studies of children of alcoholic parents and matched controls recruited from the community. Using a mixed modeling approach, we tested whether children showed elevated mother- and child-reported internalizing symptoms (a) at the same time that parents showed alcohol-related consequences (time-varying effects), (b) if parents showed greater alcohol-related consequences during the study period (proximal effects), and (c) if parents had a lifetime diagnosis of alcoholism that predated the study period (distal effects). No support for time-varying effects was found; proximal effects of mothers' alcohol-related consequences on child-reported internalizing symptoms were found and distal effects of mother and father alcoholism predicted greater internalizing symptoms among children of alcoholic parents. Implications for the time-embedded relations between parent alcoholism and children's internalizing symptoms are discussed.     

Acquisition,Extinction, Recovery,and Reversal of Different Response Sequences Under Conditional Control by Nicotine in Rats

Complex voluntary behaviors occur in sequence. Eight rats were trained in an operant procedure that used nicotine and non-drug (saline) states as interoceptive cues that signaled which of two behavioral sequences led to food reward. The distal and proximal responses in the chain were always maintained on variable interval 30-sec and fixed ratio-1 schedules, respectively, and rate differences between the responses were used as the dependent variable. Extinction and reversal training was conducted. Distal response rates were significantly greater than proximal response rates during training, testing, extinction, and reversal learning. These data suggest that (a) nicotine can establish interoceptive control over different response sequences, and (b) extinction of one response sequence may be state-dependent. The clinical relevance of extinction of complex behavioral repertoires such as drug-seeking and drug-taking behavior that are evoked by specific interoceptive cues is addressed in regard to drug abuse treatment and relapse.     

Proximal and distal effects of mortality salience on willingness to engage in health promoting behavior along the life span

The current studies examine proximal and distal mortality salience effects on the willingness to engage in health-promoting activities and explore the roles of age and self-esteem. In Study 1, 164 participants completed a self-esteem scale, were assigned to a mortality salience or a neutral condition, and then completed a scale, tapping their willingness to engage in health promoting activities. Findings revealed that in the proximal mode, mortality salience led the young and middle-aged adults to report higher willingness to promote health behaviors, whereas older adults tended to show a lower willingness to promote their health compared to the control condition. In Study 2, a total of 251 participants completed the same series of questionnaires, including a distracting task immediately after the mortality salience manipulation. Findings revealed that, in the distal mode, whereas death reminders did not affect young adults, mortality salience led middle-aged participants to express higher willingness to conduct health-promoting behaviors than in a control condition. The mortality salience induction did not affect older adults with high self-esteem, but led low self-esteem individuals to report higher willingness to promote their health. The differences between the reactions of the different age groups in both the defense modes are discussed in view of the terror management theory.     

Comparative judgments of distal size: A chronometric analysis

Observers were required to make comparative judgments of the distal sizes of squares at various perceived distances in a pictorial array. It was predicted that observers would normalize distance prior to judgment. Chronometric analyses indicated that the time to make “same” judgments increased systematically with the relative distance of the two stimuli. The time required to make “different” judgments depended on the nature of the difference. When the stimuli differed in proximal size, distal size, and distance, response time increased with distance ratio. However, when the stimuli differed in distal size and distance but not proximal size, response time decreased with distance ratio. In addition, when the stimuli differed in both distal and proximal size but not distance, RT decreased with size ratio. These results are consistent with a class of models that incorporate distance normalization into the comparative size-judging process. These and alternative models are discussed.     

Tomorrow I’ll be me: The effect of time perspective on the activation of idealistic versus pragmatic selves

It is widely accepted that the self-system is dynamic and consists of multiple selves that emerge under different contexts. The present research describes two types of diverging self-conceptions, the idealistic and pragmatic selves. Building on a synthesis of construal level theory with research on the self, we propose that a more distal time perspective activates an idealistic versus a pragmatic self. Self-activation, in turn, influences the preference between two major motives: maximizing identity versus instrumental benefits. A series of five studies supported this conceptualization by demonstrating that: (a) distal rather than proximal time perspective enhances the preference for identity over instrumental benefits; (b) people construe themselves as relatively more idealistic than pragmatic when primed with a distal than proximal time perspective, and (c) self-activation mediates the effect of time perspective on preference. The studies also investigate boundary conditions and process measures that shed light on the interface between time, self, and preference. The final section discusses the theoretical implications for the literatures on construal level, self, and justice and the practical implications for organizational behavior, political psychology, and human decision-making.     

Comprehension of human pointing gestures in horses (Equus caballus)

Twenty domestic horses (Equus caballus) were tested for their ability to rely on different human gesticular cues in a two-way object choice task. An experimenter hid food under one of two bowls and after baiting, indicated the location of the food to the subjects by using one of four different cues. Horses could locate the hidden reward on the basis of the distal dynamic-sustained, proximal momentary and proximal dynamic-sustained pointing gestures but failed to perform above chance level when the experimenter performed a distal momentary pointing gesture. The results revealed that horses could rely spontaneously on those cues that could have a stimulus or local enhancement effect, but the possible comprehension of the distal momentary pointing remained unclear. The results are discussed with reference to the involvement of various factors such as predisposition to read human visual cues, the effect of domestication and extensive social experience and the nature of the gesture used by the experimenter in comparative investigations.     

Comparison of Behavioral Belief Structures in the Physical Activity Domain

Behavioral belief structures were evaluated in the physical activity domain along 4 dimensions: positive–negative, affective–instrumental, distal–proximal, and specific motive. Participants completed 19 behavioral belief items and a measure of intention. These behavioral beliefs were subsequently classified on each dimension by 2 independent judges. Results using structural equation modeling showed that positive–negative, affective–instrumental, and proximal–distal dimensions each improved fit over a single behavioral belief construct. Division by affective–instrumental and positive–negative yielded the best fit, compared to single dimensions, but no division resulted in adequate model fit. Indeed, fit continued to improve as each dimension was added, but this specificity came with incumbent multicollinearity when trying to use the constructs for prediction purposes.     

ERK1/2 activation is necessary for BDNF to increase dendritic spine density in hippocampal CA1 pyramidal neurons

Brain-derived neurotrophic factor (BDNF) is a potent modulator of synaptic transmission and plasticity in the CNS, acting both pre- and postsynaptically. We demonstrated recently that BDNF/TrkB signaling increases dendritic spine density in hippocampal CA1 pyramidal neurons. Here, we tested whether activation of the prominent ERK (MAPK) signaling pathway was responsible for BDNF's effects on spine growth. Slice cultures were transfected with enhanced yellow fluorescent protein (eYFP) by particle-mediated gene transfer, and CA1 pyramidal neurons were imaged by laser-scanning confocal microscopy. We confirmed that BDNF (24 h) increases spine density in apical dendrites of CA1 neurons. The MEK (ERK kinase) inhibitors PD98059 and U0126 completely prevented the increase in spine density induced by BDNF, without having an effect on spine density by themselves. In contrast to its actions on cortical pyramidal neurons, BDNF had minor and rather localized effects on dendritic complexity in hippocampal pyramidal neurons, increasing the total length, but not the branching of apical dendrites within CA1 stratum radiatum, without affecting basal dendrites in stratum oriens. Our results support the hypothesis that the ERK-signaling pathway not only mediates long-term synaptic plasticity and hippocampal-dependent learning, but it is also involved in the structural remodeling of excitatory spine synapses triggered by neurotrophins.