Selective choice between double prey objects by frogs

Show me your best side: Lateralization of social and resting behaviors in feral horses

Growing evidence shows a variety of sensorial and motor asymmetries in social and non-social interactions in various species, indicating a lateralized processing of information by the brain. Using digital video cameras on tripods and drones, this study investigated lateralization in frequency and duration of social behavior patterns, in affiliative, agonistic, and resting contexts, in a feral population of horses (Equus ferus caballus) in Northern Portugal, consisting of 37 individuals organized in eight harem groups. Affiliative interactions (including grooming) were more often performed, and lasted longer, when recipients were positioned to the right side. In recumbent resting (animals lying down) episodes on the left side lasted longer. Our results of an affiliative behavior having a right side tendency, provide partial support to the valence-specific hypothesis of Ahern and Schwartz (1979) - left hemisphere dominance for positive affect, affiliative behaviors. Longer recumbent resting episodes on the left side may be due to synchronization. However, in both instances it is discussed how lateralization may be context dependent. Investigating the position asymmetries of social behaviors in feral equids will contribute to a better understanding of differential lateralization and hemispheric specialization from the ecological and evolutionary perspectives.

Long-range neural inhibition and stimulus competition in the archerfish optic tectum

The archerfish, which is unique in its ability to hunt insects above the water level by shooting a jet of water at its prey, operates in a complex visual environment. The fish needs to quickly select one object from among many others. In animals other than the archerfish, long-range inhibition is considered to drive selection. As a result of long-range inhibition, a potential target outside a neuron's receptive field suppresses the activity elicited by another potential target within the receptive field. We tested whether a similar mechanism operates in the archerfish by recording the activity of neurons in the optic tectum while presenting a target stimulus inside the receptive field and a competing stimulus outside the receptive field. We held the features of the target constant while varying the size, speed, and distance of the competing stimulus. We found cells that exhibit long-range inhibition; i.e., inhibition that extends to a significant part of the entire visual field of the animal. The competing stimulus depressed the firing rate. In some neurons, this effect was dependent on the features of the competing stimulus. These findings suggest that long-range inhibition may play a crucial role in the target selection process in the archerfish.

Selective attention without a neocortex

Selective attention refers to the ability to restrict neural processing and behavioral responses to a relevant subset of available stimuli, while simultaneously excluding other valid stimuli from consideration. In primates and other mammals, descriptions of this ability typically emphasize the neural processing that takes place in the cerebral neocortex. However, non-mammals such as birds, reptiles, amphibians and fish, which completely lack a neocortex, also have the ability to selectively attend. In this article, we survey the behavioral evidence for selective attention in non-mammals, and review the midbrain and forebrain structures that are responsible. The ancestral forms of selective attention are presumably selective orienting behaviors, such as prey-catching and predator avoidance. These behaviors depend critically on a set of subcortical structures, including the optic tectum (OT), thalamus and striatum, that are highly conserved across vertebrate evolution. In contrast, the contributions of different pallial regions in the forebrain to selective attention have been subject to more substantial changes and reorganization. This evolutionary perspective makes plain that selective attention is not a function achieved de novo with the emergence of the neocortex, but instead is implemented by circuits accrued and modified over hundreds of millions of years, beginning well before the forebrain contained a neocortex. Determining how older subcortical circuits interact with the more recently evolved components in the neocortex will likely be crucial for understanding the complex properties of selective attention in primates and other mammals, and for identifying the etiology of attention disorders.

Lateralization of Eye Use in Cuttlefish: Opposite Direction for Anti-Predatory and Predatory Behaviors

Vertebrates with laterally placed eyes typically exhibit preferential eye use for ecological activities such as scanning for predators or prey. Processing visual information predominately through the left or right visual field has been associated with specialized function of the left and right brain. Lateralized vertebrates often share a general pattern of lateralized brain function at the population level, whereby the left hemisphere controls routine behaviors and the right hemisphere controls emergency responses. Recent studies have shown evidence of preferential eye use in some invertebrates, but whether the visual fields are predominately associated with specific ecological activities remains untested. We used the European common cuttlefish, Sepia officinalis, to investigate whether the visual field they use is the same, or different, during anti-predatory, and predatory behavior. To test for lateralization of anti-predatory behavior, individual cuttlefish were placed in a new environment with opaque walls, thereby obliging them to choose which eye to orient away from the opaque wall to scan for potential predators (i.e., vigilant scanning). To test for lateralization of predatory behavior, individual cuttlefish were placed in the apex of an isosceles triangular arena and presented with two shrimp in opposite vertexes, thus requiring the cuttlefish to choose between attacking a prey item to the left or to the right of them. Cuttlefish were significantly more likely to favor the left visual field to scan for potential predators and the right visual field for prey attack. Moreover, individual cuttlefish that were leftward directed for vigilant scanning were predominately rightward directed for prey attack. Lateralized individuals also showed faster decision-making when presented with prey simultaneously. Cuttlefish appear to have opposite directions of lateralization for anti-predatory and predatory behavior, suggesting that there is functional specialization of each optic lobe (i.e., brain structures implicated in visual processing). These results are discussed in relation to the role of lateralized brain function and the evolution of population level lateralization.

The role of the dorsal thalamus in visual processing and object selection: a case of an attentional system in amphibians

In amphibians, the midbrain tectum is regarded as the visual centre for object recognition but the functional role of forebrain centres in visual information processing is less clear. In order to address this question, the dorsal thalamus was lesioned in the salamander Plethodon shermani, and the effects on orienting behaviour or on visual processing in the tectum were investigated. In a two-alternative-choice task, the average number of orienting responses toward one of two competing prey or simple configural stimuli was significantly decreased in lesioned animals compared to that of controls and sham-lesioned animals. When stimuli were presented during recording from tectal neurons, the number of spikes on presentation of a stimulus in the excitatory receptive field and a second salient stimulus in the surround was significantly reduced in controls and sham-lesioned salamanders compared to single presentation of the stimulus in the excitatory receptive field, while this inhibitory effect on the number of spikes of tectal neurons was absent in thalamus-lesioned animals. In amphibians, the dorsal thalamus is part of the second visual pathway which extends from the tectum via the thalamus to the telencephalon. A feedback loop to the tectum is assumed to modulate visual processing in the tectum and to ensure orienting behaviour toward visual objects. It is concluded that the tectum-thalamus-telencephalon pathway contributes to the recognition and evaluation of objects and enables spatial attention in object selection. This attentional system in amphibians resembles that found in mammals and illustrates the essential role of attention for goal-directed visuomotor action.

Leopard frog priorities in choosing between prey at different locations

Frogs are able to respond to a prey stimulus throughout their 360° ground-level visual field as well as in the superior visual field. We compared the likelihood of frogs choosing between a more nasally located, ground-level prey versus a more temporally located ground-level prey, when the prey at the nasal location is further away from the frog. Two crickets were presented simultaneously at 9 pairs of angles that included both crickets in the binocular visual field, both crickets in the monocular visual field, or one cricket in the binocular field and one in the monocular field. Frogs chose the more nasally located prey at least 71% of the time when the more temporal prey was in the monocular field; and 64% of the time when both prey were in the binocular field. Frogs tended to choose the more nasally located prey, even though it takes the frog longer to reach the prey. In addition, when given a choice between a prey located at ground level versus a prey located in the superior field, frogs tend to choose the prey at ground-level. These results suggest that there is a neural mechanism that biases frogs' responses to prey stimuli.

Engagement of visual fixation suppresses sensory responsiveness and multisensory integration in the primate superior colliculus

Neurons in the intermediate and deep layers of the superior colliculus (SC) often exhibit sensory-related activity in addition to discharging for saccadic eye movements. These two patterns of activity can combine so that modifications of the sensory response can lead to changes in orienting behaviour. Can behavioural factors, however, influence sensory activity? In this study of rhesus monkeys, we isolate one behavioural factor, the state of visual fixation, and examine its influences on sensory processing and multisensory integration in the primate SC. Two interleaved fixation conditions were used: a FIX condition requiring exogenous fixation of a visible fixation point; and a FIX-BLINK condition, requiring endogenous fixation in the absence of a visible fixation point. Neurons of the SC were influenced by fixation state, exhibiting both lower levels of sensory activity and reduced multisensory interactions when fixation was exogenously engaged on a visible fixation point. These results are consistent with active visual fixation suppressing responses to extraneous stimuli, and thus demonstrate that sensory processing and multisensory responses in the SC are not dependent solely on the physical properties of the sensory environment, but are also dynamically influenced by the behavioural state of the animal.

Nucleus isthmi enhances calcium influx into optic nerve fiber terminals in Rana pipiens

We examined the role of nucleus isthmi in enhancing intracellular calcium concentrations in retinotectal fibers in the frog optic tectum in vitro. The intracellular calcium levels were measured using the fluorescent calcium-sensitive dye, Calcium Green-1 3000 mw dextran conjugate (CG-1), which was injected into one optic nerve. Electrical stimulation of the labeled optic nerve alone increased tectal CG-1 fluorescence whereas electrical stimulation of nucleus isthmi alone had no effect on CG-1 fluorescence. Electrical stimulation of the nucleus isthmi ipsilateral to the labeled tectum, followed by electrical stimulation to the optic nerve can enhance calcium uptake more than a double pulse stimulation of the optic nerve alone. Maximum enhancement of the calcium signal by nucleus isthmi occurs when optic nerve stimulation follows the ipsilateral nucleus isthmi stimulation by 10 ms. These results suggest that nucleus isthmi input can facilitate retinotectal neurotransmission, and the mechanism could be used to allow the frog to attend to a single prey stimulus in an environment of several prey stimuli.

Neural modulation of visuomotor functions underlying prey-catching behaviour in anurans: perception, attention, motor performance, learning

The present review points out that visuomotor functions in anurans are modifiable and provides neurophysiological data which suggest modulatory forebrain functions. The retino-tecto/tegmento-bulbar/spinal serial processing streams are sufficient for stimulus-response mediation in prey-catching behaviour. Without its modulatory connections to forebrain structures, however, these processing streams cannot manage perceptual tasks, directed attention, learning performances, and motor skills. (1) Visual prey/non-prey discrimination is based on the interaction of this processing stream with the pretectal thalamus involving the neurotransmitter neuropeptide-Y. (2) Experiments applying the dopamine agonist apomorphine in combination with 2DG mapping and single neurone recording suggest that prey-catching strategies in terms of hunting prey and waiting for prey depend on dose dependent dopaminergic adjustments in the neural macronetwork in which retinal, pretecto-tectal, basal ganglionic, limbic, and mesolimbic structures participate. (3) Visual response properties of striatal efferent neurones support the concept that ventral striatum is involved in directed attention. (4) Various modulatory loops involving the ventral medial pallium modify prey-recognition in the course of visual or visual-olfactory learning (associative learning) or are responsible for stimulus-specific habituation (non-associative learning). (5) The circuits suggested to underlie modulatory forebrain functions are accentuated in standard schemes of the neural macronetwork. These provide concepts suitable for future decisive experiments.

Possible evolutionary origins of cognitive brain lateralization

Despite the substantial literature on the functional architecture of the asymmetries of the human brain, which has been accumulating for more than 130 years since Dax and Broca's early reports, the biological foundations of cerebral asymmetries are still poorly understood. Recent advances in comparative cognitive neurosciences have made available new animal models that have started to provide unexpected insights into the evolutionary origins and neuronal mechanisms of cerebral asymmetries. Animal model-systems, particularly those provided by the avian brain, highlight the interrelations of genetic, hormonal and environmental events to produce neural and behavioural asymmetries. Novel evidences showing that functional and structural lateralization of the brain is widespread among vertebrates (including fish, reptiles and amphibians) have accumulated rapidly. Perceptual asymmetries, in particular, seem to be ubiquitous in everyday behaviour of most species of animals with laterally placed eyes; in organisms with wider binocular overlap (e.g., amphibians), they appear to be retained for initial detection of stimuli in the extreme lateral fields. We speculate that adjustment of head position and eye movements may play a similar role in mammals with frontal vision as does the choice for right or left lateral visual fields in animals with laterally placed eyes. A first attempt to trace back the origins of brain asymmetry to early vertebrates is presented, based on the hypothesis that functional incompatibility between the logical demands associated with very basic cognitive functions is central to the phenomenon of cerebral lateralization.

Hand deviations away from visual cues: indirect evidence for inhibition

Previous research has demonstrated that when a stimulus is to be ignored, the path of motion towards a target (saccade or manual reach) deviates away from the to-be-ignored stimulus. Path deviations in saccade and reaching tasks have, however, been observed in very different situations. In the saccade tasks subjects initially attended to a cue, then disengaged attention while saccading to a target. By contrast, in the selective reaching tasks attention was continuously withdrawn from the to-be-ignored stimulus, as this was irrelevant throughout the experiment. In the two experiments reported here, cues similar to those studied in saccade tasks are examined with selective reaching procedures. Experiment 1 shows that when a coloured light-emitting diode cue, upon which subjects engage and then subsequently disengage attention, is close to the responding hand, the hand deviates away from the cue. Experiment 2 confirms this cue avoidance by showing that, compared with central fixation alone, the hand veers away from a central cue. These results confirm that the path deviations observed in saccades can also be obtained in manual reaching movements. Such findings support the notion that eye and hand movements are both affected by inhibitory mechanisms of attention.

Lateralization of predator-evasion response in a teleost fish (Girardinus falcatus)

Evidence of lateral asymmetries in the direction of turning during escape behaviour in a species of poeciliid fish, Girardinus falcatus, is reported. When repeatedly faced with a simulated predator (in five successive sessions, spaced 7 days apart), immature Girardinus falcatus exhibited a significant population bias to turn right on the first session and a progressive bias to turn left in subsequent sessions. Mature Girardinus were then tested to check whether the shift in the direction of turn with repeated sessions depended on maturation or habituation. It was found that adult Girardinus showed a slight population bias to turn right in the first session and a strong subsequent bias to turn left after repeated sessions. The implications of these findings to our current understanding of the evolution of brain lateralization are discussed.

A neural model of interactions subserving prey-predator discrimination and size preference in anuran amphibia

The model described is an extension of a previous model of the optic tectum (Arbib & Lara, 1982; Lara, Arbib & Cromarty, 1982; Lara & Arbib, 1982) and takes into consideration anatomical, physiological and behavioral studies in anurans, as well as earlier modelling efforts (Ewert & Von Seelen, 1974; Didday, 1976). Computer simulations were conducted to analyze how interactions among retina, optic tectum and pretectum may give frogs and toads the ability to discriminate between prey and predator stimuli. Results from simulations have allowed us to reproduce empirical observations, to suggest new experiments, and to postulate what neural mechanisms might be involved in some phenomena related to prey-catching orienting behavior, with direction invariance of prey-predator recognition being a consequence of tectal architecture, and size preference and response latency depending on the motivational state of the animal.

Orienting behavior of juvenile frogs with both a pre-metamorphically rotated and a normal eye

We have studied the orienting behavior of juvenile Rana pipiens in which one eye was rotated at late larval stages and the other eye left intact. Such frogs orient accurately to stimuli falling solely in the visual field of the intact eye and systematically misorient to stimuli falling solely in the field of the rotated eye. Stimuli within the area of visual field overlap elicited two distinct sets of responses, one attributable to the normal and the other to the rotated eye.

A neural model of the interaction of tectal columns in prey-catching behavior

Building on a simple model of a tectal column as the unit of processing in the amphibian tectum, we conduct a computer analysis of the interaction of a linear array of such columns. The model suggests that the inhibitory and excitatory activity in the tectum may have three functions: 1) spatio-temporal facilitation of column activity to a moving stimulus; 2) preference for the head of the stimulus, probably to avoid possible defensive reactions of the prey; and 3) modulating the state of excitation of the column once it has produced a response. The model also shows that the spatio-temporal effects of excitation and inhibition increases the acuity of the animal to the direction of the prey, through processes similar to lateral inhibition.

The visual connections of the adult flatfish, Achirus lineatus

Metamorphosis in the flatfish is characterized by the migration of one eye around the dorsal surface of the head to a position adjacent to the other eye on the new top side of the animal. The visual connections of the adult flatfish, Achirus lineatus, were examined. Either the migrating or non-migrating eye was removed and the animal allowed to survive for one to three weeks. Alternate sections of the brain were stained by a modification of the Fink-Heimer technique, or with cresyl violet. The diencephalic visual connections of the flatfish were similar to those of other teleosts with contralateral projections to the nuclei corticalis, dorsomedialis thalami, pretectalis, and the corpus geniculatum laterale. The distribution of the retinal efferents to the optic tectum is unique in the flatfish. In the medial one-third of the tectum, terminal degeneration was found in three bands in the stratum opticum (SO) and the stratum griseum et fibrosum superficiale (sgfs). In the middle part of the tectum, two bands of degeneration remained over the sgfs. The lateral part of the tectum has only a very small amount of degeneration distributed radomly in scattered clusters over the deep SO and superficial sgfs. The Nissl preparations also reflected the differences between the medial and lateral parts of the tectum. Distinct layer was lacking in the medial tectum with a conspicuously absent large cell layer in the stratum griseum centrale (sgc). In contrast, the lateral tectum had a typical tectal stratification. Most notable were the large neurons of the sgc.