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Kenneth C Catania

Publications and source records attributed to Kenneth C Catania.

8 recordsLinked to original sources
PubMed2004

Tactile foveation in the star-nosed mole.

Star-nosed moles have a specialized somatosensory system with 22 mechanosensory appendages surrounding the nostrils. A pair of appendages (the 11th pair on the ventral midline) acts as the tactile fovea and is used for detailed investigations. Here we used a high speed video camera to document movements of the star while moles searched for small prey items. Mole foraging behavior was very fast; the star, which is just over a centimeter in diameter, was touched to different areas of the environment approximately 13 times per second. This suggests that a mole foraging without interruption could potentially investigate 46,000 cm2 of surface area per hour. In 100% of 526 trials in which prey was identified and eaten, star-nosed moles made rapid, saccadic movements of the star to investigate the contacted prey with the foveal appendages. The movements of the star were similar to visual saccades in other species. Maximum velocity of the star during saccades was approximately 40 cm/s, and most saccades were between 30 and 60 ms in duration. As in the primate visual system, small corrective saccades were often needed to accurately foveate. We quantified the number of contacts different appendages made with prey items of various sizes during each encounter and compared this distribution to a previously proposed simulation of star movements during prey encounters. The behavior pattern and the simulation produced similar distributions of contact between the appendages and prey, and both distributions were closely correlated with the degree of cortical magnification of the appendage representations in primary somatosensory cortex (S1).

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PubMed2003

Organization of somatosensory cortex in the laboratory rat (Rattus norvegicus): Evidence for two lateral areas joined at the representation of the teeth.

Lateral somatosensory areas have not been explored in detail in rats, and theories on the organization of this region are based largely on anatomical tracing experiments. We investigated the topography of this region by using microelectrode recordings, which were related to flattened cortical sections processed for cytochrome oxidase (CO). Two lateral somatosensory areas were identified, each containing a complete representation of the body. A larger, more medial representation formed a mirror image of S1 along the rostrocaudal axis of the head region corresponding to the previously identified secondary somatosensory area (S2). A smaller, more lateral representation formed a mirror image of S2 along the rostrocaudal axis of the forelimb and hindlimb regions and likely corresponds to the parietal ventral area (PV) identified in other mammals. We also investigated the representation of the dentition and identified regions of cortex responsive to tooth stimulation. The lower incisor representation was rostral to the lower lip region of S1, and the upper incisor representation was lateral to the buccal pad region of S1. The upper and lower incisors flanked the tongue representation. An additional large region of far lateral cortex responded to both incisors. Finally, five CO-dense modules were consistently identified rostral and lateral to the S1 face representation, which we refer to as OM1, OM2, OM3, FM, and HM. These modules closely correspond to the physiologically identified areas representing the lower incisor (OM1) and tongue (OM2) regions of S1 and the mixed tooth (OM3), forelimb (FM1), and hindlimb (HM) representations of S2 and PV.

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PubMed2003

Somatosensation in the superior colliculus of the star-nosed mole.

The superior colliculus (or optic tectum in nonmammals) plays a critical role in the visual system and is essential for integrating sensory inputs to guide eye and head movements. However, what is the role of the superior colliculus (SC) in species that depend almost exclusively on touch? In this study we examined the SC of the star-nosed mole, a subterranean mammal that, instead of using vision, explores its environment using its tactile star. The star acts like a mechanosensory eye with a central tactile fovea that is constantly shifted in a saccadic manner. Multiunit microelectrode recordings were used to determine the topography and receptive field organization of somatosensory inputs to the SC and to test for visual and auditory responses. Here we report an SC dominated by somatosensory inputs in which neurons in all layers responded to mechanosensory stimulation, forming a topographic representation of contralateral body dominated by the mechanosensory star. Receptive fields were large, and appendage representations overlapped, suggesting that the SC may use a distributed, population code to guide the saccadic movements of the mole's touch fovea. No auditory or visual responses were recorded from the SC, although neurons in the neighboring inferior colliculus responded to auditory stimuli. Layers IVb-VII were identified, and a layer superficial to IVb contained neurons that responded to somatosensory stimulation, suggesting that there are unique patterns of afferents in the star-nosed mole's SC.

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PubMed2002

Somatosensory cortex dominated by the representation of teeth in the naked mole-rat brain.

We investigated naked mole-rat somatosensory cortex to determine how brain areas are modified in mammals with unusual and extreme sensory specializations. Naked mole-rats (Heterocephalus glaber) have numerous anatomical specializations for a subterranean existence, including rows of sensory hairs along the body and tail, reduced eyes, and ears sensitive to low frequencies. However, chief among their adaptations are behaviorally important, enlarged incisors permanently exterior to the oral cavity that are used for digging, object manipulation, social interactions, and feeding. Here we report an extraordinary brain organization where nearly one-third (31%) of primary somatosensory cortex is devoted to the representations of the upper and lower incisors. In addition, somatosensory cortex is greatly enlarged (as a proportion of total neocortical area) compared with closely related laboratory rats. Finally, somatosensory cortex in naked mole-rats encompasses virtually all of the neocortex normally devoted to vision. These findings indicate that major cortical remodeling has occurred in naked mole-rats, paralleling the anatomical and behavioral specializations related to fossorial life.

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PubMed2002

How do features of sensory representations develop?

Sensory representations in the brainstem and cortex have a number of features that support the idea that neural activity patterns are important in their development. Many of these features vary across species in ways that could result from perturbances in the balance of the effects of activity patterns and position-dependent gene expression. (1) Most notably, disruptions or septa in sensory maps often reflect actual discontinuities in the receptor sheet, and the discontinuities may be reflected in a series of interconnected maps. Species with different disruption patterns in sensory sheets have different matching disruption patterns in the sensory maps and variant individuals and strains of the same species have matching variations in the receptor disruption patterns and their sensory maps. (2) In addition, mutations that misdirect some of the retinal afferents from one side of the brain to the other create new sensory maps that preserve continuities in the altered pattern of input, while creating new structural discontinuities. (3) Furthermore, functionally different classes of afferents that are mixed in the receptor sheet often segregate to activate separate populations of target cells. (4) Finally, early developing portions of receptor sheets may gain more than their share of territory in sensory maps. These and other variable features of sensory maps are most readily accommodated by theories that involve roles for instruction by evoked and spontaneous neural activity patterns.

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PubMed2002

Receptive fields and response properties of neurons in the star-nosed mole's somatosensory fovea.

Star-nosed moles have an extraordinary mechanosensory system consisting of 22 densely innervated nasal appendages covered with thousands of sensitive touch domes. A single appendage acts as the fovea and the star is constantly shifted to touch this foveal appendage to objects of interest. Here we investigated the receptive fields on the star and the response properties of 144 neurons in the mole's primary somatosensory cortex (S1). Excitatory receptive fields were defined by recording multiunit activity from the S1 representations of the nasal appendages that form the star, while stimulating the touch domes on the skin surface with a small probe. Receptive fields were among the smallest reported for mammalian glabrous skin, averaging <1 mm(2). The smallest receptive fields were found for the fovea representation, corresponding to its greater cortical magnification. Single units were then isolated, primarily from the representation of the somatosensory fovea, and the skin surface was stimulated with a small probe attached to a piezoelectric wafer controlled by a computer interface. The response properties of neurons and the locations of inhibitory surrounds were evaluated with two complementary approaches. In the first set of experiments, single microelectrodes were used to isolate unit activity in S1, and data were collected for stimulation to different areas of the sensory star. In the second set of experiments, a multi-electrode array (4 electrodes spaced at 200 microm in a linear sequence) was used to simultaneously record from isolated units in different cortical areas representing different parts of the sensory periphery. These experiments revealed a short-latency excitatory discharge to stimulation of the fovea followed by a long-lasting suppression of spontaneous activity. Sixty-one percent of neurons responded with an excitatory OFF response at the end of the stimulus; the remaining 39% of cells did not respond or were inhibited at stimulus offset. Stimulation of areas surrounding the central receptive field often revealed inhibitory surrounds. Forty percent of the neurons that responded to mechanosensory stimulation of the receptive field center were inhibited by stimulation of surrounding areas of skin on the same appendage. In contrast to neurons in rodent barrels, few neurons within a stripe representing an appendage responded to stimulation of neighboring (nonprimary) appendages on the snout. The small receptive fields, short latencies, and inhibitory surrounds are consistent with the star's role in rapidly determining the locations and identities of objects in a complex tactile environment.

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PubMedDate not supplied

Barrels, stripes, and fingerprints in the brain - implications for theories of cortical organization.

In the last decade improvements in the histological processing of cortical tissue in conjunction with the investigation of additional mammalian species in comparative brain studies has expanded the information available to guide theories of cortical organization. Here I review some of these recent findings in the somatosensory system with an emphasis on modules related to specializations of the peripheral sensory surface. The diversity of modular representations, or cortical "isomorphs" suggest that information from the sensory sheet guides many of the features of cortical maps and suggest that cortex is not constrained to form circular units in the form of a traditional cortical column.

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