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D M Senseman

Publications and source records attributed to D M Senseman.

12 recordsLinked to original sources
PubMed1999

Modal behavior of cortical neural networks during visual processing.

The network behavior of cortical cells during the processing of a light flash was characterized in an isolated, but functionally intact, turtle visual system. Rapid changes in intracellular membrane potential were monitored optically using a voltage-sensitive dye (VSD). Spatially coherent changes in membrane potential were determined by subjecting high-speed movies of the VSD signals to Karhunen-Loéve decomposition. In all experimental trials analyzed (n > 50), coherent activity was restricted to a small number of similar spatial patterns or modes. At least four modes (M(1,1), M(1,2), M(2,1), and M(2,2)) have an organizational structure similar to the normal modes of a vibrating membrane (drum). This empirical observation of modal activity provides a useful framework for analyzing the macroscopic behavior of cortical networks.

Animals↗
PubMed1996

High-speed optical imaging of afferent flow through rat olfactory bulb slices: voltage-sensitive dye signals reveal periglomerular cell activity.

Fast, multiple-site optical recording and video imaging techniques were combined to visualize the olfactory processing stream as it flowed through rat olfactory bulb slices stained with the voltage-sensitive dye RH155. A 464 element photodiode detector array was used to record the voltage-sensitive dye signals. Focal electrical stimulation of the olfactory nerve layer evoked relatively large optical responses in the olfactory nerve and glomerular layers but only small responses within the external plexiform layer. With paired-pulse stimulation, glomerular attenuation was evident in signals recorded from the glomerular and external plexiform layers but not from the olfactory nerve layer. At very high recording speeds ( < 0.2 msec/frame), the presynaptic component of the olfactory processing stream could be followed as it flowed through the olfactory nerve layer and into the glomerular layer, where its amplitude rapidly declined. This decline was followed by a reciprocal rise in a postsynaptic depolarization that was largely restricted to the glomerular layer. Spatiotemporal interactions between overlapping afferent streams within the glomerular layer were observed and partially characterized. The optically recorded glomerular layer response was largely resistant to bath application of GABAA receptor antagonists but was sensitive to manipulations of external chloride concentration and to bath application of a stilbene derivative, 4-acetamido-4'isothiocyanatostilbene-2,2'-disulfonic acid known to block Cl- conductances. It is suggested the the voltage-sensitive dye signals recorded from the glomerular layer reflect activity in periglomerular cells and that Cl- efflux through non-GABAA chloride channels contributes to the postsynaptic depolarization of these cells after olfactory nerve stimulation.

Afferent Pathways↗
PubMed1994

Fast multisite optical recording of mono- and polysynaptic activity in the hamster suprachiasmatic nucleus evoked by retinohypothalamic tract stimulation.

Responses of the hamster suprachiasmatic nucleus (SCN) to retinohypothalamic tract (RHT) stimulation were studied in horizontal hypothalamic slices using fast multisite optical recording techniques. A 124-element photodiode detector array provided high-speed monitoring (0.5 ms/frame) of evoked neural activity in the SCN, while a larger 464-element photodiode array yielded improved spatial imaging with some loss in temporal resolution (1.6 ms/frame). Brief electrical stimulation of the optic nerves evoked a propagated compound action potential that was recorded optically as a single transient depolarization in many slice regions, including the SCN. Only within the SCN, however, was this optic tract signal followed by additional voltage-dependent optical responses which exhibited a fast and a slow depolarizing component. The initial upstroke of the fast component was Ca(2+)-insensitive and is presumed to reflect activity in presynaptic RHT afferents. The remainder of the fast depolarization and the slow depolarization were Ca(2+)-sensitive. These responses were labeled the early population excitatory postsynaptic potential (Early P.E.P.S.P.) and the Late P.E.P.S.P. respectively. The Late P.E.P.S.P. was not enhanced by K+ channel blockade, suggesting that glial depolarization is not the primary source of this component. Drugs known to suppress RHT-evoked SCN field potentials also suppressed the Early and Late P.E.P.S.P.'s recorded optically in the SCN. Unexpectedly, the Early P.E.P.S.P. was also reduced by the GABAA antagonist, bicuculline. Surface plots of normalized peak amplitudes showed that both SCN components had similar spatial distributions within the SCN, although the Early P.E.P.S.P. tended to be slightly more prominent within the medial SCN in some preparations. It is suggested that the Early P.E.P.S.P. represents firing of monosynaptically activated SCN neurons, while the Late P.E.P.S.P. reflects polysynaptic activity within the intrinsic SCN neuronal network that may be involved in the light entrainment of the circadian oscillator.

Animals↗
PubMed1987

Odor-elicited activity monitored simultaneously from 124 regions of the salamander olfactory bulb using a voltage-sensitive dye.

In response to controlled, odor pulse stimulation of the olfactory receptor mucosa, large fluorescence signals were recorded simultaneously from 124 contiguous anatomical regions of the salamander olfactory bulb using the potentiometric probe RH 414. The amplitudes and waveforms of the signals varied systematically across the bulbar surface in apparent correspondence with the laminae of the bulbar neurons. Qualitatively similar results were obtained using both intact and decorporate preparations, although fluorescence signals obtained from intact animals were distorted by optical noise generated by mechanical disturbances related to the functioning cardiovascular system. These results indicate that multiple site optical recording can be used to obtain information about spatio-temporal patterning of bulbar electrical activity evoked by physiological odor stimulation of the receptor mucosa. This is the first demonstration that activity elicited by a single, one second odor stimulus at physiological concentration and duration can be measured across many elements in the olfactory bulb. Information provided by this approach, in combination with complementary data derived from 2-deoxyglucose and single unit studies, may yield a better understanding of how the vertebrate central nervous system extracts quality and concentration information from olfactory afferent input.

Action Potentials↗
PubMed1987

MSORTV imaging of electrotonic conduction in a syncitium: optical recording of polarization spread in a simple salivary gland.

The spread of hyperpolarizing current injected into the salivary gland of the snail Helisoma trivolvis was studied with the technique of multiple site optical recording of transmembrane voltage (MSORTV). Using MSORTV it was possible to monitor simultaneously the spread of current passed by an intracellular microelectrode in up to 124 separate gland regions. Our results demonstrate the feasibility of combining conventional intracellular injection techniques with MSORTV to visualize 2-dimensional current spread in an electrical syncitium.

Animals↗
PubMed1985

Luminal and basolateral surface membranes of secretory acinar cells: electrophysiological comparison of cationic sensitivities.

Cation sensitivities (K+, Na+, and Ca2+) of luminal and basolateral membrane surfaces of secretory acinar cells were compared using a luminally perfused and externally superfused salivary gland from the aquatic snail, Helisoma trivolvis. Tight junctions delimiting the two membrane surfaces were observed near the acinar lumen suggesting that the total membrane area exposed to the superfusion solution exceeded that in contact with the luminal perfusion solution. The resting membrane potential of acinar cells was found to be dependent upon the K+ concentration in both the external superfusion and the luminal perfusion solutions. Unilateral K+ elevation at either membrane surface produced a rapid and sustained depolarization of the acinar cell. For a given K+ concentration, the level of depolarization produced by K+ elevation at the basolateral surface was significantly higher than at the luminal surface. The highest level of membrane depolarization was observed following simultaneous K+ elevation at both membrane surfaces. The ability of acinar cells to generate overshooting action potentials in response to electrical field stimulation was dependent upon both Na+ and Ca2+. Complete blockade invariably occurred following bilateral removal of either cation. The effects of unilateral removal of either Na+ or Ca2+ proved to be somewhat variable. In general, unilateral removal of Na+ was more effective in reducing the regenerative response than Ca2+ while removal of either cation from the basolateral surface was more effective in reducing the regenerative response than its removal from the luminal surface. Electrically evoked action potentials in acinar cells could also be blocked with unilateral application of the Ca2+ antagonist, cadmium (Cd2+), at either membrane surface. However, higher Cd2+ concentrations were required to achieve complete blockade when applied to the luminal than to the basolateral gland surface. This result fails to support a hypothesis of voltage-sensitive Ca2+ channels being spatially restricted to the luminal cell surface in this preparation.

Action Potentials↗
PubMed1983

Multiple-site optical recording of membrane potential from a salivary gland. Interaction of synaptic and electrotonic excitation.

The interaction between synaptic and electronic excitation of cells from the salivary gland of the snail Helisoma trivolvis was studied using a voltage-sensitive merocyanine dye. Linear and square photodiode matrix arrays were used to record simultaneously the response to neuronal stimulation of 15-25 separate regions of the gland. Laterally opposed acini exhibited highly synchronous electrical activity, which suggested a correspondingly high degree of electrical coupling. In the longitudinal direction, coupling appeared weaker. The onset of depolarization after neuronal stimulation was progressively delayed along the longitudinal gland axis, in agreement with the measured conduction velocity of the presynaptic nerve spike. In most instances, neuronal stimulation directly activated a regenerative gland response (action potential) at the junction between the anterior and central duct. Excitation of distal gland regions was usually mediated by electronic spread from active, more proximal gland regions. Occasionally, "collisions" between excitatory waves traveling in opposite directions were observed.

Action Potentials↗
PubMed1980

Electrical activity in an exocrine gland: optical recording with a potentiometric dye.

Propagated action potentials in the salivary gland of a freshwater snail were detected by optical means. Voltage-dependent absorption changes from acinar cells stained with a merocyanine-oxazolone dye faithfully reproduced the time course of electrical activity in this tissue. Such signals may provide a useful tool for the study of endocrine tissue as well.

Action Potentials↗
PubMedDate not supplied

Correspondence between visually evoked voltage-sensitive dye signals and synaptic activity recorded in cortical pyramidal cells with intracellular microelectrodes.

Fast, multiple-site optical recording of voltage-sensitive dye (VSD) signals and intracellular microelectrode recordings were combined to characterize visually evoked neuronal responses in the visual cortex of the pond turtle, Pseudemys scripta. By using an in vitro, eye-brain preparation stained with the merocyanine oxazolone voltage-sensitive dye, NK-2495 or a close analog, NK-2761, large VSD signals relatively free of vibrational noise could be recorded in single trials following a stroboscopic light flash to the contralateral eye. VSD signals recorded from the same cortical location in repeated trials exhibited considerable variability in the onset, duration, and amplitude of secondary depolarizations. Because of this variability, secondary depolarizations were largely absent in signal-averaged responses. Superposition of VSD signals with intracellular recordings obtained from cortical pyramidal cells revealed a close correspondence between their signal waveforms. The two signals were virtually identical in their onset, initial rate of rise, and time-to-peak. At later periods (> 500 ms), the correspondence was less close, especially for large cortical depolarizations. Some of this disparity could be attributed to contamination of the VSD signal by a large intrinsic optical response. A second contribution was a failure of the VSD signal to register asynchronous regenerative effects occurring in single pyramidal cells. It is suggested that the close correspondence between the microelectrode and optical recordings in the early phase of the response may reflect the organization of pyramidal cells into clusters that receive virtually identical synaptic inputs.

Animals↗
PubMedDate not supplied

Spatiotemporal structure of depolarization spread in cortical pyramidal cell populations evoked by diffuse retinal light flashes.

The spatiotemporal structure of cortical activity evoked by diffuse light flashes was investigated in an isolated eyecup-brain preparation of the pond turtle, Pseudemys scripta. By combining a photomicroscopic image of the preparation with voltage-sensitive dye signals recorded by a 464-element photodiode array, the spread of depolarization within different cortical areas could be directly visualized with millisecond temporal resolution. Diffuse stimulation of the contralateral eyecup initially depolarized the visual cortex at the junction between its lateral and medial divisions in a small area rostral of the ventricular eminence. From this point, the depolarization spread at different velocities (10-100 microm/ms) depending upon the direction of travel. Since the initial depolarization was always in the rostral pole, the largest spread invariably occurred in a rostral --> caudal direction. Within the confines of the medial visual cortex, depolarization spread at a constant velocity but slowed after entering the adjoining medial cortex. Increasing the stimulus illuminance increased the velocity of spread. Rostrocaudal spread of depolarization was also observed in response to electrical stimulation of the geniculocortical pathway and by direct focal stimulation of the cortical sheet. These data suggest that excitatory connections between pyramidal cell clusters play a prominent role in the initial activation of the cortex by diffuse retinal stimulation.

Animals↗
PubMedDate not supplied

Optical recording of action potentials from vertebrate nerve terminals using potentiometric probes provides evidence for sodium and calcium components.

Optical methods are shown to monitor action potentials from a population of nerve terminals in the neurohypophysis of Xenopus. Calcium antagonists such as cadmium and nickel ions block a component of the action potential that probably reflects a calcium-mediated potassium conductance, and tetrodotoxin blocks an inward sodium current, revealing a calcium component to the action potential upstroke.

Action Potentials↗