Multisensory integration supports configural learning of a home refuge in the whip spider Phrynus marginemaculatus

ABSTRACTWhip spiders (Amblypygi) reside in structurally complex habitats and are nocturnally active yet display notable navigational abilities. From the theory that uncertainty in sensory inputs should promote multisensory representations to guide behavior, we hypothesized that their navigation is supported by a multisensory and perhaps configural representation of navigational inputs, an ability documented in a few insects and never reported in arachnids. We trained Phrynus marginemaculatus to recognize a home shelter characterized by both discriminative olfactory and tactile stimuli. In tests, subjects readily discriminated between shelters based on the paired stimuli. However, subjects failed to recognize the shelter in tests with either of the component stimuli alone. This result is consistent with the hypothesis that the terminal phase of their navigational behavior, shelter recognition, can be supported by the integration of multisensory stimuli as an enduring, configural representation. We hypothesize that multisensory learning occurs in the whip spiders' extraordinarily large mushroom bodies, which may functionally resemble the hippocampus of vertebrates.

Multisensory Configural Learning of a Home Refuge in the Whip Spider Phrynus marginemaculatus

ABSTRACTWhip spiders (Amblypygi) reside in structurally complex habitats and are nocturnally active yet display notable navigational abilities. From the theory that uncertainty in sensory inputs should promote multisensory representations to guide behavior, we hypothesized that their navigation is supported by a configural, multisensory representation of navigational inputs, an ability documented in a few insects and never reported in arachnids. We trained Phrynus marginemaculatus to recognize a home shelter characterized by both discriminative olfactory and tactile stimuli. In tests, subjects readily discriminated between shelters based on the paired stimuli. However, subjects failed to recognize the shelter in tests with either of the component stimuli alone. This result is consistent with the hypothesis that the terminal phase of their navigational behavior, shelter recognition, can be supported by the integration of multisensory stimuli as a configural representation. We hypothesize that multisensory configural learning occurs in the whip spiders’ extraordinarily large mushroom bodies, which may functionally resemble the hippocampus of vertebrates.

Discriminable Height Differences of Raised Lines

Introduction: The purpose of this study was to determine the discriminable height differences of raised lines printed on paper, as assessed by people who are blind, with or without years of tactile experience. Methods: Ten younger and 10 older tactile readers with blindness and with rich tactile experience; and 10 blindfolded, older, sighted participants with little tactile experience discriminated paired raised-line stimuli of different heights using the fingers of their preferred hand by active touch in a psychophysical experiment. Results: There was a significant main effect of the height of the stimulus, F(2, 54) = 56.446, MS = .060, p < .001, [Formula: see text] = .676, [Formula: see text] = .341, and participant group, F(2, 27) = 13.717, MS = .064, p < .001, [Formula: see text] = .504, [Formula: see text] = .357; however, there was no significant main effect of the width of the lines, or any interactions. The younger and older tactile readers had virtually similar thresholds and Weber fractions, and they could discriminate paired stimuli more accurately and efficiently than the older, sighted participants. We provided the discriminable height data of the raised lines based on the mean and 95th percentile values of the Weber fractions. Discussion: The results indicate the importance of tactile experiences for height discrimination in active touch. For older persons with recently developed blindness, raised lines with larger height differences should be used. Information for practitioners: These data will be helpful for developing new braille embossers that can print raised-line graphics for people with visual impairments, with or without years of tactile experience.

Phasic dopamine enhances the distinct decoding and perceived salience of stimuli

Subjects learn to assign value to stimuli that predict outcomes. Novelty, rewards or punishment evoke reinforcing phasic dopamine release from midbrain neurons to ventral striatum that mediates expected value and salience of stimuli in humans and animals. It is however not clear whether phasic dopamine release is sufficient to form distinct engrams that encode salient stimuli within these circuits. We addressed this question in awake mice. Evoked phasic dopamine induced plasticity selectively to the population encoding of coincidently presented stimuli and increased their distinctness from other stimuli. Phasic dopamine thereby enhanced the decoding of previously paired stimuli and increased their perceived salience. This dopamine-induced plasticity mimicked population coding dynamics of conditioned stimuli during reinforcement learning. These findings provide a network coding mechanism of how dopaminergic learning signals promote value assignment to stimulus representations.

Why Does George Clooney Make Coffee Sexy? The Case for Attribute Conditioning

When a celebrity (e.g., George Clooney) endorses a brand (e.g., a coffee type), people’s assessment of this brand typically changes. We suggest that the mere repeated pairing of celebrities with brands imbues brands with the celebrities’ attributes. We call this effect attribute conditioning, which is, more generally, the phenomenon that people assess a stimulus’s attributes differently as a results of its pairing with another stimulus possessing that attribute. We review evidence showing that this effect goes beyond evaluative-conditioning effects, that it is not a demand effect, and that it is easily shown with many attributes (e.g., sexy, athletic, healthy) and many different stimuli (e.g., faces, shapes, brand logos). In addition, we review process evidence supporting the hypothesis that the effect is based on a memory structure that links the mental representations of the paired stimuli. We conclude with a brief outline of possible applied (e.g., marketing) and theoretical avenues for further research.