GABAergic inputs to the nucleus rotundus (pulvinar inferior) of the pigeon (Columba livia)

The ectostriatum is a large visual structure in the avian telencephalon. Part of the tectofugal pathway, the ectostriatum receives a large ascending thalamic input from the nucleus rotundus, the homolog of the mammalian pulvinar complex. We investigated the effects of bilateral lesions of the ectostriatum in pigeons on visual motion and spatial-pattern perception tasks. To test motion perception, we measured performance on a task requiring detection of coherently moving random dots embedded in dynamic noise. To test spatialpattern perception, we measured performance on the detection of a square wave grating embedded in static noise. A double dissociation was revealed. Pigeons with lesions to the caudal ectostriatum showed a performance deficit on the motion task but not the grating task. In contrast, pigeons with lesions to the rostral ectostriatum showed a performance deficit on the grating task but not the motion task. Thus, in the avian telencephalon, there is a separation of visual motion and spatial-pattern perception as there is in the mammalian telencephalon. However, this separation of function is in the targets of the tectofugal pathway in pigeons rather than in the thalamofugal pathway as described in mammals. The implications of these findings with respect to the evolution of the visual system are discussed. Specifically, we suggest that the principle of parallel visual streams originated in the tectofugal pathway rather than the thalamofugal pathway.

Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 73%

A Dissociation of Motion and Spatial-Pattern Vision in the Avian Telencephalon: Implications for the Evolution of “Visual Streams”

Nguyen¹,

Spetch²,

Crowder³

et al. 2004

“…This asymmetry suggests that the E in barn owls is mainly involved in visual and not auditory processing. Because we did not systematically survey the E, we cannot rule out the possibility that it is functionally divided into subregions with different modality preferences, consistent with the idea that the tectofugal pathway is functionally segregated (Benowitz and Karten, 1976;Mpodozis et al, 1996;Karten et al, 1997). Despite the relatively weak influence of auditory signals alone, congruent auditory stimuli presented simultaneously with the visual stimuli substantially enhanced the visual SSA effects.…”

Section: Discussionmentioning

confidence: 99%

Interactions between Stimulus-Specific Adaptation and Visual Auditory Integration in the Forebrain of the Barn Owl

Reches¹,

Netser²,

Gutfreund³

2010

Neural adaptation and visual auditory integration are two well studied and common phenomena in the brain, yet little is known about the interaction between them. In the present study, we investigated a visual forebrain area in barn owls, the entopallium (E), which has been shown recently to encompass auditory responses as well. Responses of neurons to sequences of visual, auditory, and bimodal (visual and auditory together) events were analyzed. Sequences comprised two stimuli, one with a low probability of occurrence and the other with a high probability. Neurons in the E tended to respond more strongly to low probability visual stimuli than to high probability stimuli. Such a phenomenon is known as stimulus-specific adaptation (SSA) and is considered to be a neural correlate of change detection. Responses to the corresponding auditory sequences did not reveal an equivalent tendency. Interestingly, however, SSA to bimodal events was stronger than to visual events alone. This enhancement was apparent when the visual and auditory stimuli were presented from matching locations in space (congruent) but not when the bimodal stimuli were spatially incongruent. These findings suggest that the ongoing task of detecting unexpected events can benefit from the integration of visual and auditory information.

“…This parceling into parallel pathways originates in the OT in which different subclasses of TGCs project to separate regions in nRt (Benowitz and Karten, 1976;Mpodozis et al, 1996;Karten et al, 1997;Marín et al, 2003). It is possible that the bimodal information we report here is originating in a subclass of multisensory TGCs and is transferred alongside other visual pathways.…”

Section: The Avian Tectofugal Pathwaymentioning

confidence: 99%

Auditory and Multisensory Responses in the Tectofugal Pathway of the Barn Owl

Reches¹,

Gutfreund²

2009

A common visual pathway in all amniotes is the tectofugal pathway connecting the optic tectum with the forebrain. The tectofugal pathway has been suggested to be involved in tasks such as orienting and attention, tasks that may benefit from integrating information across senses. Nevertheless, previous research has characterized the tectofugal pathway as strictly visual. Here we recorded from two stations along the tectofugal pathway of the barn owl: the thalamic nucleus rotundus (nRt) and the forebrain entopallium (E). We report that neurons in E and nRt respond to auditory stimuli as well as to visual stimuli. Visual tuning to the horizontal position of the stimulus and auditory tuning to the corresponding spatial cue (interaural time difference) were generally broad, covering a large portion of the contralateral space. Responses to spatiotemporally coinciding multisensory stimuli were mostly enhanced above the responses to the single modality stimuli, whereas spatially misaligned stimuli were not. Results from inactivation experiments suggest that the auditory responses in E are of tectal origin. These findings support the notion that the tectofugal pathway is involved in multisensory processing. In addition, the findings suggest that the ascending auditory information to the forebrain is not as bottlenecked through the auditory thalamus as previously thought.