Rapid structural chances in nerve fibers evoked by electric current pulses

Tasaki, Ichiji; Byrne, Paul M.

doi:10.1016/0006-291x(92)91092-5

Cited by 78 publications

(60 citation statements)

References 11 publications

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“…Cell swelling has also been reported to occur during normal neuronal activity, but with a negligible amplitude that is much smaller than that caused by prolonged and strong depolarization (44,56,(65)(66)(67)(68). In general, the displacements of the cell surface are on the length scale of nanometers, with a maximum displacement of several tens of nanometers, under normal electrical stimulation (65)(66)(67)(68).…”

Section: Discussionmentioning

confidence: 99%

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Assessing the sensitivity of diffusion MRI to detect neuronal activity directly

Bai

Stewart

Plenz

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Functional MRI (fMRI) is widely used to study brain function in the neurosciences. Unfortunately, conventional fMRI only indirectly assesses neuronal activity via hemodynamic coupling. Diffusion fMRI was proposed as a more direct and accurate fMRI method to detect neuronal activity, yet confirmative findings have proven difficult to obtain. Given that the underlying relation between tissue water diffusion changes and neuronal activity remains unclear, the rationale for using diffusion MRI to monitor neuronal activity has yet to be clearly established. Here, we studied the correlation between water diffusion and neuronal activity in vitro by simultaneous calcium fluorescence imaging and diffusion MR acquisition. We used organotypic cortical cultures from rat brains as a biological model system, in which spontaneous neuronal activity robustly emerges free of hemodynamic and other artifacts. Simultaneous fluorescent calcium images of neuronal activity are then directly correlated with diffusion MR signals now free of confounds typically encountered in vivo. Although a simultaneous increase of diffusion-weighted MR signals was observed together with the prolonged depolarization of neurons induced by pharmacological manipulations (in which cell swelling was demonstrated to play an important role), no evidence was found that diffusion MR signals directly correlate with normal spontaneous neuronal activity. These results suggest that, whereas current diffusion MR methods could monitor pathological conditions such as hyperexcitability, e.g., those seen in epilepsy, they do not appear to be sensitive or specific enough to detect or follow normal neuronal activity.D eveloping a direct MRI method to detect neuronal activity in vivo and noninvasively is a major focus in neuroscience. Progress in this area is required to improve our understanding of normal brain function, and in a clinical setting, to develop new tools for studying normal and abnormal development to diagnose diseases and disorders of the brain. Functional MRI (fMRI) has been widely used in the cognitive neurosciences since its invention in the 1990s (1-3). The most widely used fMRI method, blood-oxygenation-level-dependent (BOLD) MRI, detects hemodynamic changes in the brain, which only indirectly reflects neuronal activity. Moreover, its hemodynamic origin limits both its spatial and temporal resolution and its interpretation as a direct proxy for neuronal activity (4, 5).More recently, several MRI methods were proposed to provide more direct measures of neuronal excitation (6). In particular, diffusion MRI, a method to measure the apparent diffusivity of water within tissues (7-9), has been suggested as a direct functional imaging method to detect neuronal activity (10-13). Early in vivo experiments in both humans and animals reported small but significant increases in highly diffusion-weighted MRI signals, which were ascribed to changes directly induced by the underlying neuronal activity rather than indirect hemodynamic changes (10-13).In vitro experimen...

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Section: Discussionmentioning

confidence: 99%

“…In general, the displacements of the cell surface are on the length scale of nanometers, with a maximum displacement of several tens of nanometers, under normal electrical stimulation (65)(66)(67)(68). However, the surface displacement changes in the neuronal soma induced by prolonged depolarization can be ≥∼1 μm (44,56,57).…”

Section: Discussionmentioning

confidence: 99%

Assessing the sensitivity of diffusion MRI to detect neuronal activity directly

Bai

Stewart

Plenz

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…56,57,[60][61][62][63] Multiple physiological processes, such as neurotransmitter secretion, 64 reorientation of membrane proteins and phospholipids, 56,57,65 and refractive index change of neural tissues 66 during neural activation, might contribute to the observed IOSs observed in neural tissues. Water influx in response to ionic currents through gated channels during depolarization causes cellular swelling, which can also produce light scattering 61,62,67,68 and polarization changes 63 in stimulus-activated excitable cells.…”

Section: Discussionmentioning

confidence: 99%

Stimulus-evoked outer segment changes in rod photoreceptors

et al. 2016

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Abstract. Rod-dominated transient retinal phototropism (TRP) has been recently observed in freshly isolated mouse and frog retinas. Comparative confocal microscopy and optical coherence tomography revealed that the TRP was predominantly elicited from the rod outer segment (OS). However, the biophysical mechanism of rod OS dynamics is still unknown. Mouse and frog retinal slices, which displayed a cross-section of retinal photoreceptors and other functional layers, were used to test the effect of light stimulation on rod OSs. Time-lapse microscopy revealed stimulus-evoked conformational changes of rod OSs. In the center of the stimulated region, the length of the rod OS shrunk, while in the peripheral region, the rod OS swung toward the center region. Our experimental observation and theoretical analysis suggest that the TRP may reflect unbalanced rod disc-shape changes due to localized visible light stimulation.

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“…After using a succession of ionic blockades to alter flow across membranes, they hypothesized that increased neural discharge results in cell swelling, causing increased light transmission. A recent study by Tasaki and Byrne (1992) demonstrated that rapid swelling and shrinking of nerve fibers upon stimulation occurred on the time order of action potentials. They showed that displacement of the nerve surface, an increase in the pressure exerted by the nerve surface, and a reduction of reflected light intensity all occur in conjunction with an increase in water content upon electrical stimulation of the fibers.…”

Section: Histologymentioning

confidence: 99%

“…In addition, several activityrelated processes have disparate time courses. Glial cell swelling (Kimelberg and Frangakis, 1985;Walz and Hinks, 1985) and increases in blood volume following heightened neural activity (Frostig et al, 1990) occur over a few seconds, while neuronal cell volume (Tasaki and Byrne, 1992) changes (Landowne, 1992) which are usually associated with action potentials, develop on the order of milliseconds. We measured scattered light (660 or 700 nm), which is principally affected by neural and glial volume variations between states and incorporates both fast (milliseconds) and slow (seconds) processes.…”

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confidence: 99%

Hippocampal reflected optical patterns during sleep and waking states in the freely behaving cat

1994

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We examined reflected light as a measure of neural activity from a 2 mm2 area of dorsal hippocampus and surrounding neocortex in nine freely behaving cats during sleep and waking states. Light reflectance at 660 or 700 nm was measured by a coherent fiber optic probe attached to a charge-coupled device video camera that allowed acquisition of images from subcortical structures. In the dorsal hippocampus, rapid eye movement sleep (REMS) and active waking (AW) resulted in a significant decline (-0.9% +/- 0.3 and -2.0% +/- 0.5, respectively) in overall reflected light from the dorsal hippocampus relative to quiet sleep (QS), while quiet waking (QW) resulted in an overall increase (+2.0% +/- 0.4). In the neocortical probe placement group, reflectance also decreased during AW (-1.6% +/- 0.5) and increased during QW (+1.7 +/- 0.6) as compared to QS. In contrast to the hippocampus, however, overall reflectance increased, rather than decreased, in the neocortex during REMS (+2.7% +/- 1.3). We interpret a decline in reflectance as representing increased activation of underlying neural tissue. Thus, the cat dorsal hippocampus increased overall activity during REMS as compared to QS, while neocortical structures decreased overall activity during the same state. These results concur with expected activity changes based on electrophysiologic and autoradiographic studies. The imaging procedure provided a continuous assessment of spatially organized neural activity changes in the freely behaving animal.

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Rapid structural chances in nerve fibers evoked by electric current pulses

Cited by 78 publications

References 11 publications

Assessing the sensitivity of diffusion MRI to detect neuronal activity directly

Assessing the sensitivity of diffusion MRI to detect neuronal activity directly

Stimulus-evoked outer segment changes in rod photoreceptors

Hippocampal reflected optical patterns during sleep and waking states in the freely behaving cat

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