Object discrimination performance and dynamics evaluated by inferotemporal cell population activity

We have previously reported an increase in response tolerance of inferotemporal cells around trained views. However, an inferotemporal cell usually displays different response patterns in an initial response phase immediately after the stimulus onset and in a late phase from approximately 260 ms after stimulus onset. This study aimed to understand the difference between the two time periods and their involvement in the view-invariant object recognition. Responses to object images with and without prior experience of object discrimination across views, recorded by microelectrodes, were pooled together from our previous experiments. With a machine learning algorithm, we trained to build classifiers for object discrimination. In the early phase, the performance of classifiers created based on data of responses to the object images with prior training of object discrimination across views did not significantly differ from that based on data of responses to the object images without prior experience of object discrimination across views. However, the performance was significantly better in the late phase. Furthermore, compared to the preferred stimulus image in the early phase, we found 2/3 of cells changed their preference in the late phase. For object images with prior experience of training with object discrimination across views, a significant higher percentage of cells responded in the late phase to the same objects as in the early phase, but under different views. The results demonstrate the dynamics of selectivity changes and suggest the involvement of the late phase in the view-invariant object recognition rather than that of the early phase.

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Inferotemporal cells respond to the presentation of stimulus image in two phases.

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Two thirds of cells change their stimulus preferences between the two phases.

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Object discrimination leads better performance of classifier in the late phase.

An intrinsic algorithm for viewing angle tolerance of object discrimination in human subjects

Prevailing theories suggest that view-invariant object recognition is accomplished via spatiotemporal correlations of multiple views that bind different views to the same object. However, it is unknown how the exposure to multiple views without association affects view-invariant recognition generating. Behavioural studies have shown that monkeys acquired view-invariant object recognition capability in a range of the viewing angles of 30° to 60° after experiencing discrimination of similar objects at each of several viewing angles without associating different views, but the monkeys could not discriminate novel objects from similar distractors when the viewing angle changed. In the present study the development of the view invariance was tested in the human subjects and compared with the results of the monkeys previously reported. The view-invariant object recognition capability of human subjects was tested using either familiar objects that the subjects experienced in a preparatory object discrimination task at the same viewpoints or novel objects that the subjects had never experienced. In the viewing angle range of 30°, human subjects showed significant object discrimination capability across views, with no need for prior experience of the objects. Prior discrimination experience within the same viewpoints endowed the human subjects with broadening of the viewing angle tuning, because an object discrimination test immediately after the prior discrimination experience at a single view showed wider viewing angle tuning than a test without prior experience. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Difference in the generalization of response tolerance across views between the anterior and posterior part of the inferotemporal cortex

The inferotemporal cortex consists of an anterior (cytoarchitectonic area TE) and a posterior (area TEO) part, which together constitute the final areas of the ventral visual stream, which is critical for object discrimination. Area TE receives dense projections from area TEO. We have previously identified a response tolerance in the cells in area TE in monkeys to a range of viewing angles after object discrimination at each of several views. To investigate the contribution of area TEO to the establishment of such a response tolerance in area TE, we conducted electrophysiological recordings of the responses of the single cells in area TEO after performance saturation of object discrimination at several independent views, without any association across views, and compared them with those obtained from the TE cells. The cells in area TEO showed responses to the experienced object views, but not to nearby views. Comparisons of the tunings of the TE and TEO cells to different viewing angles for the same object sets in the same animal showed that cells in area TEO had a significantly narrower tuning width, whereas the response tolerance was usually observed in the TE cells across viewing angles up to 60°. Our findings revealed a significant difference in the representation of the object views between areas TE and TEO, and suggested that such a representation in area TE may be completed through neuronal mechanisms within area TE, which is not a property of the earlier stages of the ventral visual stream.

Differences in spatial and temporal frequency interactions between central and peripheral parts of the feline area 18

The visual system demonstrates significant differences in information processing abilities between the central and peripheral parts of the visual field. Optical imaging based on intrinsic signals was used to investigate the difference in stimulus spatial and temporal frequency interactions related to receptive field eccentricity in the cat area 18. Changing either the spatial or the temporal frequency of grating stimuli had a significant impact on responses in the cortical areas corresponding to the centre of the visual field and more peripheral parts at 10 degrees eccentricity. The cortical region corresponding to the centre of the gaze was tuned to 0.4 cycles per degree (c/deg) for spatial frequency and 2 Hz for temporal frequency. In contrast, the cortical region corresponding to the periphery of the visual field was tuned to a lower spatial frequency of 0.15 c/deg and a higher temporal frequency of 4 Hz. Interestingly, when we simultaneously changed both the spatial frequency and the temporal frequency of the grating stimuli, the responses were significantly different from those estimated with an assumption of independence between the spatial and temporal frequency in the cortical region corresponding to the periphery of the visual field. However, in the cortical area corresponding to the centre of the gaze, spatial frequency showed significant independence from temporal frequency. These properties support the notion of relative specialization of visual information processing for peripheral representations in cortical areas.

Dynamics of population coding for object views following object discrimination training

We have previously demonstrated that inferotemporal neurons respond to objects viewed from a range of angles, even without any prior experience in learning the associations among the views. Several models have been proposed to explain object recognition across disparate views. However, direct neuronal evidence is rare. In the present study, we focused on the response similarity of a population of inferotemporal cells to object views, following different prior experiences. Two monkeys were subjected to a task in which object discrimination across views was required. We found significantly higher neural response similarity to 30° separated views, 190ms after object image presentation, than without any prior discrimination experience across views. The time period over which the similarity was significant began and endured similarly for 60° separated views at 190-850ms. For 90° separated views, the time period over which the similarity was significant was shorter and started later, at 230-550ms. The results demonstrate the dynamics of cell population activity and suggest a possible explanation for object recognition across disparate views.

Organization of local interneurons in optic glomeruli of the dipterous visual system and comparisons with the antennal lobes

The lateral protocerebrum of the fly's brain is composed of a system of optic glomeruli, the organization of which compares to that of antennal lobe glomeruli. Each optic glomerulus receives converging axon terminals from a unique ensemble of optic lobe output neurons. Glomeruli are interconnected by systems of spiking and nonspiking local interneurons that are morphologically similar to diffuse and polarized local interneurons in the antennal lobes. GABA-like immunoreactive processes richly supply optic glomeruli, which are also invaded by processes originating from the midbrain and subesophageal ganglia. These arrangements support the suggestion that circuits amongst optic glomeruli refine and elaborate visual information carried by optic lobe outputs, relaying data to long-axoned neurons that extend to other parts of the central nervous system including thoracic ganglia. The representation in optic glomeruli of other modalities suggests that gating of visual information by other sensory inputs, a phenomenon documented from the recordings of descending neurons, could occur before the descending neuron dendrites. The present results demonstrate that future studies must consider the roles of other senses in visual processing.

Morphological and optical properties of the corneal lens and retinal structure in the posterior large stemma of the tiger beetle larva

The morphological and optical features of the corneal lens and retina have been examined in the posterior large stemma of the larva of the tiger beetle (Cicindela chinensis). A cup-shaped retina was positioned 55+/-6microm beneath the posterior margin of the corneal lens, which was 479+/-20microm in diameter and 391+/-18microm in thickness (n=41). A light path through an isolated corneal lens showed that the object at infinite distance was focused on the distal margin of the retina. Geometrical optics gave a value of 334+/-15microm (n=55) for the posterior focal length of the corneal lens. The refractive index of the corneal lens was estimated to be around 1.8, if the lens was considered to be homogenous in structure. The internal structure of the lens, including concentric lamellae, was presumed to contribute to such a high refractive index, because this was higher than that of insect cuticle. The retinal structure and how images were blurred at different focus levels were also examined. Data obtained for optics of the corneal lens and retinal structures are discussed with reference to the distinct visual behavior of the larva.

Visual system of calliphorid flies: organization of optic glomeruli and their lobula complex efferents

Reconstructions of silver-stained brains revealed 27 optic glomeruli that occupy a major volume of the lateral protocerebrum. Axons from different morphological types of columnar output neurons from the lobula complex sort out to specific glomeruli. Glomeruli are partially enwrapped by glial processes and are invaded by the dendrites and terminals of local interneurons that connect different glomeruli in a manner analogous to local interneurons in the antennal lobes. Each type of columnar neuron contributes to a palisade-like ensemble that extends across the whole or a circumscribed area of the retinotopic mosaic. A second class of outputs from the lobula comprises wide-field neurons, the dendrites of which interact with planar fields or column-like patches of retinotopic inputs from the medulla. These neurons also send their axons to optic glomeruli. Dye fills demonstrate that lobula complex neurons supplying glomeruli do not generally terminate directly on descending neurons. Local interneurons and projection neurons provide integrative circuitry within and among glomeruli. As exemplified by the anterior optic tubercle, optic glomeruli can also have elaborate internal architectures. The results are discussed with respect to the identification of motion- and orientation-selective neurons at the level of the lobula and lateral protocerebrum and with respect to the evolutionary implications raised by the existence of neural arrangements serving the compound eyes, which are organized like neuropils serving segmental ganglia equipped with appendages.

Visual system of calliphorid flies: motion- and orientation-sensitive visual interneurons supplying dorsal optic glomeruli

Intracellular recordings accompanied by dye fills were made from neurons associated with optic glomeruli in the lateral protocerebrum of the brain of the blowfly Phaenicia sericata. The present account describes the morphology of these cells and their electrophysiological responses to oriented bar motion. The most dorsal glomeruli are each supplied by retinotopic efferent neurons that have restricted dendritic fields in the lobula and lobula plate of the optic lobes. Each of these lobula complex cells represents a morphologically identified type of neuron arranged as an ensemble that subtends the entire monocular visual field. Of the four recorded and filled efferent types, three were broadly tuned to the orientation of bar stimuli. At the level of optic glomeruli a relay neuron extending centrally from optic foci and a local interneuron that arborizes among glomeruli showed narrow tuning to oriented bar motion. The present results are discussed with respect to the behavioral significance of oriented motion discrimination by flies and other insects, and with respect to neuroanatomical data demonstrating the organization of deep visual neuropils.

Responses of medulla neurons to illumination and movement stimuli in the tiger beetle larvae

Intracellular responses of medulla neurons (second-order visual interneurons) have been examined in the tiger beetle larva. The larva possesses six stemmata on either side of the head, two of which are much larger than the remaining four. Beneath the cuticle housing the stemmata an optic neuropil complex occurs consisting of lamina and medulla neuropils. Response patterns of medulla neurons to illumination and moving objects varied from neurons to neurons. For movement stimuli black discs and a black bar were moved in the rostro-caudal direction above the larva. Comparison of responses to the discs and the bar suggested a spatial summation of responses in some neurons, and tuning to small objects in some neurons. The majority of neurons responded to objects moving at heights of 10 mm and 50 mm with the same discharge pattern. A few neurons, however, showed distance sensitivities responding with an increase of spike discharges to moving objects only at either of the two heights. Such distance sensitivities still remained in one-stemma larvae, three of the four stemmata being occluded. These data are discussed in relation to distinct visual behavior of the larva and with special reference to perception of the hunting range.

Behavioural responses of the tiger beetle larva to moving objects: role of binocular and monocular vision

The larva of the tiger beetle Cicindela chinensis is an ambushing hunter with a body length of 15–22 mm that lives in a tunnel in the ground. It ambushes prey, keeping its head horizontal at the opening of the tunnel. When prey approaches the tunnel, the larva jumps to snap at it. When an object moves beyond its jumping range (approximately 15 mm), however, the larva quickly withdraws deep into the tunnel. These responses are mediated by two of six pairs of stemmata. How does the larva judge the hunting range using such a simple visual system? A previous study suggested that both binocular and monocular vision are used for distance estimation. Range estimation by binocular vision was further confirmed in the present behavioural observations: larvae jumped towards objects beyond the normal hunting range when virtual images of such distant objects were formed close to the larva using prisms or a narrow window. A possible mechanism involved in range estimation by monocular vision was also examined in behavioural experiments. The depth of the image in the retina appears to play a role in distance estimation because a larva with one functional stemma, the other stemmata being occluded, changed its response to a very distant object from an escape to a predatory jump when a concave lens was placed above its head. Two alternative ideas, based on optical and morphological data, are proposed to explain this behavioural change by the one-stemma larvae. First, as for myopic people, the larva might see clearly only objects that are close. Second, an infinitely distant object might produce a focused image only on the central part of the retina, whereas an object within hunting range (<15 mm) might do so on surrounding regions of the retina. The latter idea implies that the region of the retina at which the larva perceives a clear image is concerned with which type of behaviour is released, a predatory jump or an escape. We conclude that visual information about hunting range in the tiger beetle larva is extracted both peripherally by the spatial pattern of image clarity and centrally by binocular vision.

Community based health care in the Philippine highlands: the Hanunuo Mangyans of Mindoro

The feasibility and effectiveness of community participation in the planning and delivery of health care services among the Hanunuo Mangyans in the Philippine highlands is described. The Hanunuo are swidden cultivators and one of seven indigenous ethnic minorities in the forested interior of Mindoro island. Previous Mangyan studies have shown that they have poor health, are generally malnourished and continually susceptible to communicable diseases. The need to develop viable strategies to counter their health problems is pressing since Mindoro suffers from insufficient health care facilities and personnel, and health services are rarely available to Mangyans. Baseline surveys on the health and nutritional status of the Hanunuo population in the project site indicated that the following illnesses are most prevalent: upper respiratory tract infection, skin diseases, parasitism, anaemia and malaria. The more significant health problems of the Hanunuo include poor environmental sanitation, lack of medical personnel and drugs, inadequate knowledge of curative and preventive care, lack of adequate prenatal care, poor nutritional status and lack of health education. Also described are the participation of the community in project planning and decision making, the training workshops and resource manual for the community volunteers, the coverage areas and assigned tasks of the health workers, and the organisation of village health committees.