Differences in the neuronal correlation between the central and peripheral vision in the cat early visual cortex.

Significant surround modulation was reported in the cortical areas corresponding to the periphery of the visual field, whereas no clear surround modulation was reported in the center. To understand the neural bases underlying the differences of the functions between the cortical areas corresponding to the center and periphery of the visual field, responses of the cells in the cat early visual cortex with their receptive fields in the center and periphery of the visual field were recorded by using multichannel electrodes, and cross-correlations of the spikes in the responses to the full-field stimuli, and the center-surround stimuli, which contained a grating in a central patch and a surround grating, were analyzed. Percentages of the cell pairs showing significant cross-correlation were larger in the cortical areas corresponding to the periphery than the center. In the center of the visual field, the percentages of the cell pairs showing significant cross-correlation significantly decreased as the separation of the recording points increased, and the time lags of the peaks of the cross-correlogram distributed around zero. In the periphery of the visual field, the time lags of the peaks of the cross-correlogram distributed more widely and increased as the separation of the recording points increased. In the responses to the center-surround stimuli in the preferred orientation of each cell, percentages of the cell pairs showing significant cross-correlation were larger in the periphery than the center. These results suggest that more lateral interactions occur in the cortical areas corresponding to the periphery than the center of the visual field.

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.

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.

Electrophysiological evidence for separation between human face and non-face object processing only in the right hemisphere.

Scalp event-related potential (ERP) studies have demonstrated larger N170 amplitudes when subjects view faces compared to items from object categories. Extensive attempts have been made to clarify face selectivity and hemispheric dominance for face processing. The purpose of this study was to investigate hemispheric differences in N170s activated by human faces and non-face objects, as well as the extent of overlap of their sources. ERP was recorded from 20 subjects while they viewed human face and non-face images. N170s obtained during the presentation of human faces appeared earlier and with larger amplitude than for other category images. Further source analysis with a two-dipole model revealed that the locations of face and object processing largely overlapped in the left hemisphere. Conversely, the source for face processing in the right hemisphere located more anterior than the source for object processing. The results suggest that the neuronal circuits for face and object processing are largely shared in the left hemisphere, with more distinct circuits in the right hemisphere.

Neural substrates of view-invariant object recognition developed without experiencing rotations of the objects.

One fails to recognize an unfamiliar object across changes in viewing angle when it must be discriminated from similar distractor objects. View-invariant recognition gradually develops as the viewer repeatedly sees the objects in rotation. It is assumed that different views of each object are associated with one another while their successive appearance is experienced in rotation. However, natural experience of objects also contains ample opportunities to discriminate among objects at each of the multiple viewing angles. Our previous behavioral experiments showed that after experiencing a new set of object stimuli during a task that required only discrimination at each of four viewing angles at 30° intervals, monkeys could recognize the objects across changes in viewing angle up to 60°. By recording activities of neurons from the inferotemporal cortex after various types of preparatory experience, we here found a possible neural substrate for the monkeys' performance. For object sets that the monkeys had experienced during the task that required only discrimination at each of four viewing angles, many inferotemporal neurons showed object selectivity covering multiple views. The degree of view generalization found for these object sets was similar to that found for stimulus sets with which the monkeys had been trained to conduct view-invariant recognition. These results suggest that the experience of discriminating new objects in each of several viewing angles develops the partially view-generalized object selectivity distributed over many neurons in the inferotemporal cortex, which in turn bases the monkeys' emergent capability to discriminate the objects across changes in viewing angle.

Surround modulation in cortical orientation map revealed by optical imaging and its dependency on receptive field eccentricity.

Optical imaging was used to investigate the difference in surround modulation on orientation map related to receptive field eccentricity in cat visual cortex. Presentation of center-surround stimuli at the center of gaze resulted in no clear surround modulation; however, significant modulation was observed in its corresponding cortical area when the center-surround stimuli were presented at 10° eccentricity in more peripheral parts of the visual field. Modulation was observed both in the response magnitude and in the spatial pattern of the response. Surround orientation perpendicular to the orientation of a center patch grating showed the largest modulation in the response magnitude. The modulation became weaker as the orientation difference between the center and surround gratings became smaller. Regardless of the orientations for the central patch gratings, a similar response spatial pattern was observed in the cortical region where the underlying cells had their receptive fields covering the central patch, if the stimuli were with the same surround gratings. These properties support the notion of a relative specialization for visual information processing in peripheral representations of cortical areas.

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.

Intracellular responses of antennal chordotonal sensilla of the American cockroach.

The responses of mechanoreceptor neurons in the antennal chordotonal organ have been examined in cockroaches by intracellular recording methods. The chordotonal organ was mechanically stimulated by sinusoidal movement of the flagellum. Stimulus frequencies were varied between 0.5 and 150 Hz. Receptor neurons responded with spike discharges to mechanical stimulation, and were classed into two groups from plots of their average spike frequencies against stimulus frequency. Neurons in one group responded to stimulation over a wide frequency range (from 0.5 to 150 Hz), whereas those in a second group were tuned to higher frequency stimuli. The peak stimulus frequency at which receptor neurons showed maximum responses differed from cell to cell. Some had a peak response at a stimulus frequency given in the present study (from 0.5 to 150 Hz), whereas others were assumed to have peak responses beyond the highest stimulus frequency examined. The timing for the initiation of spikes or of a burst of spikes plotted against each stimulus cycle revealed that spike generation was phase-locked in most cells. Some cells showed phase-independent discharges to stimulation at lower frequency, but increasing stimulus frequencies spike initiation began to assemble at a given phase of the stimulus cycle. The response patterns observed are discussed in relation to the primary process of mechanoreception of the chordotonal organ.

Foraging navigation of hornets studied in natural habitats and laboratory experiments.

Foraging flights have been studied in three species of hornets (Vespa mandarinia, V. simillima and V. analis) in the field and the laboratory. Hornets seem to use multiple navigational cues for visiting a familiar feeding place. They could orient towards the feeding place immediately after they rose in air from the nest without directly viewing the feeder. They could visit the feeding place after dark at a luminosity 8 lux. These data suggest that they can navigate for some distance with few external cues. Hornets also seem to rely on visual cues for their mid-range navigation. They used some structures on their way as navigational landmarks to negotiate. Individual hornets are supposed to have their own landmarks. Olfactory cues seem to be used to find a new feeding place or to recruit other member. In the approach flight hornets seemed to use multiple visual cues such as the visual characteristics of the feeder and the wider scenery around the feeder. Even if the feeder in training was removed during the test, they flew with a smooth course as if they were pin-pointing the missing feeder, but without sitting on the ground. Hornets learnt how to fly to reach the feeder without external cues after passing by the last visual landmark under conditions with extremely poor visual cues. The present work suggests that hornets retain multiple navigational cues during repeated foraging behavior, and which cues they use seems to depend upon environmental conditions.