Previous Behavioral Work Research Articles

Separate Coding of Different Gaze Directions in the Superior Temporal Sulcus and Inferior Parietal Lobule

SummaryElectrophysiological recording in the anterior superior temporal sulcus (STS) of monkeys has demonstrated separate cell populations responsive to direct and averted gaze 1, 2. Human functional imaging has demonstrated posterior STS activation in gaze processing, particularly in coding the intentions conveyed by gaze 3, 4, 5, 6, but to date has provided no evidence of dissociable coding of different gaze directions. Because the spatial resolution typical of group-based fMRI studies (∼6–10 mm) exceeds the size of cellular patches sensitive to different facial characteristics (1–4 mm in monkeys), a more sensitive technique may be required. We therefore used fMRI adaptation, which is considered to offer superior resolution [7], to investigate whether the human anterior STS contains representations of different gaze directions, as suggested by non-human primate research. Subjects viewed probe faces gazing left, directly ahead, or right. Adapting to leftward gaze produced a reduction in BOLD response to left relative to right (and direct) gaze probes in the anterior STS and inferior parietal cortex; rightward gaze adaptation produced a corresponding reduction to right gaze probes. Consistent with these findings, averted gaze in the adapted direction was misidentified as direct. Our study provides the first human evidence of dissociable neural systems for left and right gaze.

OMP gene deletion results in an alteration in odorant-induced mucosal activity patterns.

Previous behavioral work, using a complex five-odorant identification task, demonstrated that olfactory marker protein (OMP) is critically involved in odor processing to the extent that its loss results in an alteration in odorant quality perception. Exactly how the lack of OMP exerts its influence on the perception of odorant quality is unknown. However, there is considerable neurophysiological evidence that different odorants produce different spatiotemporal patterns of neural activity at the level of the mucosa and that these patterns predict the psychophysically determined perceptual relationship among odorants. In this respect, OMP gene deletion is known to result in a constellation of physiologic defects (i.e., marked reduction in the electroolfactogram (EOG) and altered response and recovery kinetics) that would be expected to alter the odorant-induced spatiotemporal activity patterns that are characteristic of different odorants. This, in turn, would be expected to alter the spatiotemporal patterning of information that results from the mucosal projection onto the bulb, thereby changing odorant quality perception. To test the hypothesis that odorant-induced mucosal activity patterns are altered in mice lacking the gene for OMP, we optically recorded the fluorescent changes in response to odorant stimulation from both the septum and turbinates of both OMP-null and control mice using a voltage-sensitive dye (di-4-ANEPPS Molecular Probes, Eugene, OR) and a Dalsa 120 x 120, 12-bit CCD camera. To maintain continuity with the previous behavioral work, the odorants 2-propanol, citral, carvone, ethylacetoacetate, and propyl acetate were again used. Each odorant was randomly presented to each mucosal surface in a Latin-Square design. The results of this study demonstrated that, for both mouse strains, there do indeed exist different spatiotemporal activity patterns for different odorants. More importantly, however, these patterns significantly differed between OMP-null and control mice. That is, although the general regions of characteristic activity for different odorants were the same in both mouse strains, the patterns in the null animals were degraded relative to controls. These data suggest therefore that the alterations in mucosal activity may serve as the substrate for the behaviorally observed changes in odorant quality perception in the null mutant.

Worker policing in the European hornet Vespa crabro

Although generally capable of producing males, workers in most hymenopteran societies (bees, ants and wasps) perform little or no reproduction in the presence of the queen. We investigated why workers do not reproduce in the European hornet Vespa crabro (L.). Previous genetic and behavioural work on this species had shown that, although queen mating frequency is low (effective paternity, 1.1) causing workers to be more related to workers' sons than to the queen's sons, workers do not lay eggs and the males reared are all the queen's sons. This suggested that workers are under queen pheromonal control. Here we show that this is not the case. Using egg introduction experiments, we show that worker policing behaviour occurs. We introduced queen-laid and worker-laid eggs into four discriminator colonies in five trials. In colonies with a queen, workers removed significantly more worker-laid than queen-laid eggs (1/79 worker-laid eggs but 46/72 queen-laid eggs remained after 16 h, p < 0.001). In colonies without a queen, workers removed significantly more queen-laid than worker laid eggs (30/44 worker-laid eggs but 13/41 queen-laid eggs remained after 16 h, p≤ 0.001). The presence of worker policing in queenright hornet colonies provides a proximate explanation for the absence of worker reproduction. Workers are not under queen control but instead are collectively enforcing their own sterility. Worker policing at low paternity may have been selected for because it enhances colony productivity by eliminating costly conflicts over reproduction.

Responses of Movement-Sensitive Visual Interneurons to Prey-Like Stimuli in the Praying Mantis Sphodromantis lineola (Burmeister)

Previous behavioral work using both mechanical and computer-generated visual stimuli has demonstrated that mantids use a computational algorithm to recognize prey similar to that used by some amphibian predators: A stimulus elicits prey capture behavior if it falls within a perceptual envelope defined by five fundamental stimulus parameters: (1) overall size, (2) length of the leading edge, (3) contrast to the background, (4) location in the visual field, and (5) apparent speed. In this study, we recorded simultaneously from both cervical nerve cords of monocular Sphodromantis lineola while they viewed the same visual stimuli successfully used in the behavioral studies. Extracellular recordings showed three consistently proportioned amplitude classes of movement-elicited spikes in each cord and these were repeatedly and reliably identifiable across mantids. Overall, the movement-elicited activity in both cords was dominated by very large spikes suggesting the existence of several large, descending movement-sensitive interneurons projecting both ipsilaterally and contralaterally from the optic lobes. However, only the largest contralateral spikes occurred preferentially to prey-like stimuli, mirrored the behavioral response curves generated by S. lineola to the same visual stimuli, and displayed activity peaks that were correlated with the times at which the mantid emitted predatory strikes.

Chemoreception of amino acids by female fourth‐ and sixth‐instar larvae of the spruce budworm

AbstractAn electrophysiological approach was used to record the responses of maxillary styloconic sensilla of fourth‐ and sixth‐instar larvae of the spruce budworm Choristoneura fumiferana to 14 amino acids. One cell in the lateral styloconic sensillum was identified as an amino acid‐sensitive neuron. All of the amino acids tested, except l‐proline and l‐arginine, were detected by this cell. Arginine did not evoke a response from either the medial or lateral styloconic sensilla. Proline evoked responses from a cell in the medial styloconic sensillum. It is known from previous behavioural work that l‐proline is a phagostimulant and l‐valine inhibits feeding in Choristoneura; we thus further characterized the responses to these two amino acids. For both instars, l‐proline was detected as low as 0.001 mmol/l and the maximal response was at 50 mmol/l. Stimulation of fourth‐ and sixth‐instar larvae with l‐valine showed that the maximum firing frequency was obtained at 1 mmol/l. Above and below this concentration, firing frequency decreases. Sensory responses to the amino acids stimuli did not correlate with known behavioral responses to similar stimuli.

Colour discrimination in goldfish

Goldfish were trained to discriminate between blue, green, and red painted panels, which varied greatly in brightness. The stimuli were chosen in such a way that the discriminations could not be solved in terms of brightness. All the discriminations were easily learnt by the fish, in spite of the large brightness differences. The results also suggest that the goldfish has a preference for blue, since the blue-green discrimination was learnt significantly faster when blue was the positive stimulus than when green was the positive stimulus. The results are considered in relation to previous physiological and behavioural work on this species. The finding that green can be discriminated from both blue and red shows that colour vision must be at least trichromatic in this species.