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Integrative Synchronization Mechanisms and Models in the Cognitive Neurosciences
Published in Harald Maurer, Cognitive Science, 2021
First of all, it should be noted that there are two complementary perspectives from which to approach neural coding (Trappenberg 2010, Brown et al. 2004, Eliasmith 2009). One can approach neural coding from the analysis of the "encoding process" (Dayan and Abbott 2001, Rieke et al. 1997). This describes the response of one or more neurons as a function of certain physical environment variables, the "stimulus", using the generation of neural action potentials (Dayan and Abbott 2001, Brown et al. 2004). Alternatively, one can approach neural coding from the analysis of the "decoding process" (Dayan and Abbott 2001, Rieke et al. 1997). This describes the (estimated) reconstruction of the originally coded stimulus (or specific aspects thereof) from a sequence of action potentials using decoding algorithms (at least, in principle).
Advances in Neuroprosthetics
Published in Chang S. Nam, Anton Nijholt, Fabien Lotte, Brain–Computer Interfaces Handbook, 2018
The hippocampus converts short-term memory to long-term memory in a process involving recoding sensory input and neural coding patterns. Therefore, the ability to form long-term, or episodic, memories can be diminished or eradicated if the hippocampus is damaged as a result of physical trauma, or is otherwise compromised by, for example, the brain receiving inadequate oxygen, certain forms of epilepsy, or neural tissue inflammation. However, in a significant demonstration of what neuroprosthetics can achieve, a neuroprosthesis based on hippocampal structure and function has been previously shown to effectively restore the ability to form long-term memory in laboratory rats (Berger et al. 2011)—and subsequently demonstrated both the first successful neuroprosthesis to enhance and/or repair memory encoding in primates (Hampson et al. 2013) and, ultimately, a successful USC/DARPA trial with human patients suffering from trauma-induced hippocampal dysfunction (Reardon 2015) that led to the start-up company Kernel (kernel.co) being founded to commercialize the hippocampal prosthesis.
Auditory nerve
Published in Stanley A. Gelfand, Hearing, 2017
Various stimuli are used to provide different kinds of information about neural coding. Clicks (at least ideally) are discrete and instantaneous in time, with energy distributed equally throughout the frequency range. On the other hand, pure tones (also ideally) extend indefinitely in time, but are discrete in frequency. Thus, click stimuli lend themselves to the study of the temporal characteristics of the discharge pattern, while sinusoids can be used to study frequency-related aspects. Tone bursts can be used to investigate both frequency and temporal characteristics, since they are similar to clicks in their duration and to tones in their frequency specificity (Kiang, 1975). One should remember, however, that a tone burst is a compromise between the two extremes, so that it is really less discrete in time than a click and less discrete in frequency than a pure tone.
Advances in Neuroscience, Not Devices, Will Determine the Effectiveness of Visual Prostheses
Published in Seminars in Ophthalmology, 2021
Bardia Abbasi, Joseph F. Rizzo
Despite our limitations in both engineering and knowledge of neural coding, it might seem surprising that current devices have had any meaningful success. Perhaps neural plasticity—the ability of the brain to modify its function based upon learning or adaptation—enables the brain to extract value from suboptimal stimuli. The best evidence that neural plasticity may provide such leverage can be gleaned from recipients of cochlear implants, who often initially report metallic, monotonous, and inscrutable sounds, but can frequently hear well enough to hold telephone conversations with long-term rehabilitative training (often up to 1 year in duration).102 In contrast, despite restoration of normal optics in patients treated for early vision loss from corneal injury or congenital cataracts, deficits in complex visual processing (such as identification of three-dimensional forms or gender classification) can persist.103–105 Some such patients have even found their restored visual input frightening or disappointing.105,106 Clearly, the success of any visual prosthetic will depend upon central reorganization following prolonged blindness.
Influence of subcortical auditory processing and cognitive measures on cocktail party listening in younger and older adults
Published in International Journal of Audiology, 2019
Chandni Jain, Vikas Mysore Dwarakanath, Amritha G
Brainstem response to complex auditory stimuli such as speech (syllable) has two classes of separate time-locked responses, transient and sustained which mimic the acoustic characteristics of the speech signal (Skoe and Kraus 2010). It has shown to provide the information regarding the auditory processing of speech signal at the subcortical level; however, based on the constraints of the phase locking properties of the brainstem, the neural coding would be limited to the second formant frequency (F2) of the signal. The sustained portion of speech auditory brainstem response (speech ABR) has shown to provide information regarding the neural response to the harmonic portion of the stimuli (periodic in nature) namely Frequency Following Response (FFR) which reflects the neural phase locking of the stimulus. Here, magnitude and timing measures become important wherein the timing measures would provide information on how the brainstem synchronously responds to the acoustic stimulus. Also, the temporal measures such as the stimulus-response correlations and quiet to noise correlations would provide information on how precisely the response mimics the stimulus and the effect of background noise on response waveform (Russo et al. 2004).
A potential neurophysiological correlate of electric-acoustic pitch matching in adult cochlear implant users: Pilot data
Published in Cochlear Implants International, 2018
Chin-Tuan Tan, Brett A. Martin, Mario A. Svirsky
As a result of this position-frequency mismatch, unilateral CI users with contralateral residual hearing need to both adapt to the frequency mismatch in the implanted ear and integrate the acoustic information from the non-implanted ear when they listen. The existence of this group of CI users permits direct matching of the pitch perceived in response to stimulation of intracochlear electrodes to the pitch elicited by an acoustic frequency. This measure (electric-acoustic pitch matching) can be useful to determine whether listeners show adaptation to the frequency mismatch described above after different amounts of listening experience with the CI (Francart et al., 2008; McDermott et al., 2009; Reiss et al., 2007, 2008, 2014, 2015; Svirsky et al., 2012; Tan et al., 2012; Vermeire et al., 2015). The neural basis for this type of adaptation may involve a combination of basic neural encoding in the auditory system and additional higher level processing. In a previous study (Tan et al., 2017), we showed that the pitch-matching functions obtained in 16 CI subjects were generally 0.9–1.2 octaves lower than the spiral ganglion functions and 0.2–0.27 octaves higher than the FAT functions, much closer to the FAT functions than the spiral ganglion functions. These findings are consistent with the possibility that adaptation to the frequency-position function imposed by CIs is not always complete. The present study examines a potential neurophysiological correlate of electric-acoustic pitch matching by examining scalp-recorded auditory evoked potentials (AEPs) in unilateral CI subjects when they are presented with alternating stimulation to one intracochlear electrode and different acoustic tones, some of which were pitch matched to the stimulation electrode while others were not.