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Smith TJ, Srinivasan H, Jiang M, Tahmasebi G, Vargas S, Villafranca LR, Tirumala Kumara S, Ogundipe A, Massaquoi A, Chandna S, Mehretab Y, Shipurkar R, Haghighi P, Cogan SF, Hernandez-Reynoso AG, Pancrazio JJ. Investigating the spatial limits of somatotopic and depth-dependent sensory discrimination stimuli in rats via intracortical microstimulation. Front Neurosci 2025; 19:1602996. [PMID: 40438624 PMCID: PMC12116559 DOI: 10.3389/fnins.2025.1602996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2025] [Accepted: 04/29/2025] [Indexed: 06/01/2025] Open
Abstract
The somatosensory cortex can be electrically stimulated via intracortical microelectrode arrays (MEAs) to induce a range of vibrotactile sensations. While previous studies have employed multi-shank MEA configurations to map somatotopic relationships, the influence of cortical depth on sensory discrimination remains relatively unexplored. In this study, we introduce a novel approach for investigating the spatial limits of stimulation-evoked sensory discrimination based on cortical depth and somatotopic relationships in rodents. To achieve this, we implanted single-shank and four-shank 16-channel MEAs into the primary somatosensory cortex of male rats. Then, we defined distinct stimulation patterns for comparison, each consisting of four simultaneously stimulated electrode sites separated along the length of the single-shank device or between shanks for the four-shank device. Next, we utilized a nose-poking, two-choice sensory discrimination task to evaluate each rat's ability to accurately differentiate between these patterns. We demonstrate that the rats were able to reliably discriminate between the most superficial (450-750 μm) and deepest (1650-1950 μm) single-shank patterns with 90% accuracy, whereas discrimination between the most superficial and next adjacent pattern (650-950 μm) significantly dropped to 53% (p < 0.05). Similarly, in the four-shank group, discrimination accuracy was 88% for the furthest pattern pairs (375 μm difference) but significantly fell to 62% (p < 0.05) for the closest pairs (125 μm difference). Overall, the single-shank subjects could robustly differentiate between stimuli separated by 800 μm along a cortical column whereas, the multi-shank animals could robustly differentiate between stimuli delivered from shanks separated by 250 μm. Results showed that when spatial distances between stimuli patterns were decreased, the rats had reduced discriminable accuracy, suggesting greater difficulty when differentiating closely positioned stimuli. To better understand the single-shank results, we also utilized computational modeling to compare our in-vivo results against neuronal activation volumes presented in a biophysically realistic model of the somatosensory cortex. These simulations displayed overlapping volumes of activated neurons via antidromic propagation of axons for the closest pattern pair, potentially influencing discriminable limits. This work, which offers insight into how the physical separation of stimulating microelectrode sites maps to discernable percepts, informs the design considerations for future intracortical microstimulation arrays.
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Affiliation(s)
- Thomas J. Smith
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Hari Srinivasan
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Madison Jiang
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Ghazaal Tahmasebi
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Sophia Vargas
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Luisa R. Villafranca
- Department of Biology, The University of Texas at Dallas, Richardson, TX, United States
| | - Shreya Tirumala Kumara
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Ashlynn Ogundipe
- Department of Healthcare Studies, The University of Texas at Dallas, Richardson, TX, United States
| | - Ajaree Massaquoi
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Shreya Chandna
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Yovia Mehretab
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Riya Shipurkar
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Pegah Haghighi
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Stuart F. Cogan
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Ana G. Hernandez-Reynoso
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - Joseph J. Pancrazio
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
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Orlemann C, Boehler C, Kooijmans RN, Li B, Asplund M, Roelfsema PR. Flexible Polymer Electrodes for Stable Prosthetic Visual Perception in Mice. Adv Healthc Mater 2024; 13:e2304169. [PMID: 38324245 PMCID: PMC11468866 DOI: 10.1002/adhm.202304169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/01/2024] [Indexed: 02/08/2024]
Abstract
Brain interfaces that can stimulate neurons, cause minimal damage, and work for a long time will be central for future neuroprosthetics. Here, the long-term performance of highly flexible, thin polyimide shanks with several small (<15 µm) electrodes during electrical microstimulation of the visual cortex, is reported. The electrodes exhibit a remarkable stability when several billions of electrical pulses are applied in vitro. When the devices are implanted in the primary visual cortex (area V1) of mice and the animals are trained to detect electrical microstimulation, it is found that the perceptual thresholds are 2-20 microamperes (µA), which is far below the maximal currents that the electrodes can withstand. The long-term functionality of the devices in vivo is excellent, with stable performance for up to more than a year and little damage to the brain tissue. These results demonstrate the potential of thin floating electrodes for the long-term restoration of lost sensory functions.
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Affiliation(s)
- Corinne Orlemann
- Department of Vision and CognitionNetherlands Institute for NeuroscienceRoyal Netherlands Academy of Arts and SciencesAmsterdam1105 BAThe Netherlands
| | - Christian Boehler
- Department of Microsystems Engineering (IMTEK)University of Freiburg79110FreiburgGermany
- BrainLinks‐BrainTools CenterUniversity of Freiburg79110FreiburgGermany
| | - Roxana N. Kooijmans
- Department of Vision and CognitionNetherlands Institute for NeuroscienceRoyal Netherlands Academy of Arts and SciencesAmsterdam1105 BAThe Netherlands
- Institute for Neuroscience and Medicine (INM‐1)Forschungszentrum Jülich52428JülichGermany
| | - Bingshuo Li
- Department of Vision and CognitionNetherlands Institute for NeuroscienceRoyal Netherlands Academy of Arts and SciencesAmsterdam1105 BAThe Netherlands
| | - Maria Asplund
- Department of Microsystems Engineering (IMTEK)University of Freiburg79110FreiburgGermany
- BrainLinks‐BrainTools CenterUniversity of Freiburg79110FreiburgGermany
- Department of Microtechnology and NanoscienceChalmers University of TechnologyGothenburg412 96Sweden
| | - Pieter R. Roelfsema
- Department of Vision and CognitionNetherlands Institute for NeuroscienceRoyal Netherlands Academy of Arts and SciencesAmsterdam1105 BAThe Netherlands
- Laboratory of Visual Brain TherapySorbonne UniversitéInstitut National de la Santé et de la Recherche MédicaleCentre National de la Recherche ScientifiqueInstitut de la VisionParisF‐75012France
- Department of Integrative NeurophysiologyCentre for Neurogenomics and Cognitive ResearchVU UniversityAmsterdam1081 HVThe Netherlands
- Department of NeurosurgeryAmsterdam University Medical CenterUniversity of AmsterdamAmsterdam1105 AZThe Netherlands
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Wu GK, Ardeshirpour Y, Mastracchio C, Kent J, Caiola M, Ye M. Amplitude- and frequency-dependent activation of layer II/III neurons by intracortical microstimulation. iScience 2023; 26:108140. [PMID: 37915592 PMCID: PMC10616374 DOI: 10.1016/j.isci.2023.108140] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 07/27/2023] [Accepted: 10/02/2023] [Indexed: 11/03/2023] Open
Abstract
Intracortical microstimulation (ICMS) has been used for the development of brain machine interfaces. However, further understanding about the spatiotemporal responses of neurons to different electrical stimulation parameters is necessary to inform the design of optimal therapies. In this study, we employed in vivo electrophysiological recording, two-photon calcium imaging, and electric field simulation to evaluate the acute effect of ICMS on layer II/III neurons. Our results show that stimulation frequency non-linearly modulates neuronal responses, whereas the magnitude of responses is linearly correlated to the electric field strength and stimulation amplitude before reaching a steady state. Temporal dynamics of neurons' responses depends more on stimulation frequency and their distance to the stimulation electrode. In addition, amplitude-dependent post-stimulation suppression was observed within ∼500 μm of the stimulation electrode, as evidenced by both calcium imaging and local field potentials. These findings provide insights for selecting stimulation parameters to achieve desirable spatiotemporal specificity of ICMS.
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Affiliation(s)
- Guangying K. Wu
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Yasaman Ardeshirpour
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Christina Mastracchio
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Jordan Kent
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
- Scientific Publications Department, Society for Neuroscience, Washington DC, USA
| | - Michael Caiola
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
| | - Meijun Ye
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD 20993, USA
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Smith TJ, Wu Y, Cheon C, Khan AA, Srinivasan H, Capadona JR, Cogan SF, Pancrazio JJ, Engineer CT, Hernandez-Reynoso AG. Behavioral paradigm for the evaluation of stimulation-evoked somatosensory perception thresholds in rats. Front Neurosci 2023; 17:1202258. [PMID: 37383105 PMCID: PMC10293669 DOI: 10.3389/fnins.2023.1202258] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 05/22/2023] [Indexed: 06/30/2023] Open
Abstract
Intracortical microstimulation (ICMS) of the somatosensory cortex via penetrating microelectrode arrays (MEAs) can evoke cutaneous and proprioceptive sensations for restoration of perception in individuals with spinal cord injuries. However, ICMS current amplitudes needed to evoke these sensory percepts tend to change over time following implantation. Animal models have been used to investigate the mechanisms by which these changes occur and aid in the development of new engineering strategies to mitigate such changes. Non-human primates are commonly the animal of choice for investigating ICMS, but ethical concerns exist regarding their use. Rodents are a preferred animal model due to their availability, affordability, and ease of handling, but there are limited choices of behavioral tasks for investigating ICMS. In this study, we investigated the application of an innovative behavioral go/no-go paradigm capable of estimating ICMS-evoked sensory perception thresholds in freely moving rats. We divided animals into two groups, one receiving ICMS and a control group receiving auditory tones. Then, we trained the animals to nose-poke - a well-established behavioral task for rats - following either a suprathreshold ICMS current-controlled pulse train or frequency-controlled auditory tone. Animals received a sugar pellet reward when nose-poking correctly. When nose-poking incorrectly, animals received a mild air puff. After animals became proficient in this task, as defined by accuracy, precision, and other performance metrics, they continued to the next phase for perception threshold detection, where we varied the ICMS amplitude using a modified staircase method. Finally, we used non-linear regression to estimate perception thresholds. Results indicated that our behavioral protocol could estimate ICMS perception thresholds based on ~95% accuracy of rat nose-poke responses to the conditioned stimulus. This behavioral paradigm provides a robust methodology for evaluating stimulation-evoked somatosensory percepts in rats comparable to the evaluation of auditory percepts. In future studies, this validated methodology can be used to study the performance of novel MEA device technologies on ICMS-evoked perception threshold stability using freely moving rats or to investigate information processing principles in neural circuits related to sensory perception discrimination.
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Affiliation(s)
- Thomas J. Smith
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Yupeng Wu
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Claire Cheon
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Arlin A. Khan
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Hari Srinivasan
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
| | - Jeffrey R. Capadona
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Advanced Platform Technology Center, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, United States
| | - Stuart F. Cogan
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Joseph J. Pancrazio
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Crystal T. Engineer
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, United States
- Texas Biomedical Device Center, The University of Texas at Dallas, Richardson, TX, United States
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5
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Smith TJ, Wu Y, Cheon C, Khan AA, Srinivasan H, Capadona JR, Cogan SF, Pancrazio JJ, Engineer CT, Hernandez-Reynoso AG. Behavioral Paradigm for the Evaluation of Stimulation-Evoked Somatosensory Perception Thresholds in Rats. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.04.537848. [PMID: 37205577 PMCID: PMC10187227 DOI: 10.1101/2023.05.04.537848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Intracortical microstimulation (ICMS) of the somatosensory cortex via penetrating microelectrode arrays (MEAs) can evoke cutaneous and proprioceptive sensations for restoration of perception in individuals with spinal cord injuries. However, ICMS current amplitudes needed to evoke these sensory percepts tend to change over time following implantation. Animal models have been used to investigate the mechanisms by which these changes occur and aid in the development of new engineering strategies to mitigate such changes. Non-human primates are commonly the animal of choice for investigating ICMS, but ethical concerns exist regarding their use. Rodents are a preferred animal model due to their availability, affordability, and ease of handling, but there are limited choices of behavioral tasks for investigating ICMS. In this study, we investigated the application of an innovative behavioral go/no-go paradigm capable of estimating ICMS-evoked sensory perception thresholds in freely moving rats. We divided animals into two groups, one receiving ICMS and a control group receiving auditory tones. Then, we trained the animals to nose-poke - a well-established behavioral task for rats - following either a suprathreshold ICMS current-controlled pulse train or frequency-controlled auditory tone. Animals received a sugar pellet reward when nose-poking correctly. When nose-poking incorrectly, animals received a mild air puff. After animals became proficient in this task, as defined by accuracy, precision, and other performance metrics, they continued to the next phase for perception threshold detection, where we varied the ICMS amplitude using a modified staircase method. Finally, we used non-linear regression to estimate perception thresholds. Results indicated that our behavioral protocol could estimate ICMS perception thresholds based on ∼95% accuracy of rat nose-poke responses to the conditioned stimulus. This behavioral paradigm provides a robust methodology for evaluating stimulation-evoked somatosensory percepts in rats comparable to the evaluation of auditory percepts. In future studies, this validated methodology can be used to study the performance of novel MEA device technologies on ICMS-evoked perception threshold stability using freely moving rats or to investigate information processing principles in neural circuits related to sensory perception discrimination.
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Urdaneta ME, Kunigk NG, Peñaloza-Aponte JD, Currlin S, Malone IG, Fried SI, Otto KJ. Layer-dependent stability of intracortical recordings and neuronal cell loss. Front Neurosci 2023; 17:1096097. [PMID: 37090803 PMCID: PMC10113640 DOI: 10.3389/fnins.2023.1096097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 03/13/2023] [Indexed: 04/08/2023] Open
Abstract
Intracortical recordings can be used to voluntarily control external devices via brain-machine interfaces (BMI). Multiple factors, including the foreign body response (FBR), limit the stability of these neural signals over time. Current clinically approved devices consist of multi-electrode arrays with a single electrode site at the tip of each shank, confining the recording interface to a single layer of the cortex. Advancements in manufacturing technology have led to the development of high-density electrodes that can record from multiple layers. However, the long-term stability of neural recordings and the extent of neuronal cell loss around the electrode across different cortical depths have yet to be explored. To answer these questions, we recorded neural signals from rats chronically implanted with a silicon-substrate microelectrode array spanning the layers of the cortex. Our results show the long-term stability of intracortical recordings varies across cortical depth, with electrode sites around L4-L5 having the highest stability. Using machine learning guided segmentation, our novel histological technique, DeepHisto, revealed that the extent of neuronal cell loss varies across cortical layers, with L2/3 and L4 electrodes having the largest area of neuronal cell loss. These findings suggest that interfacing depth plays a major role in the FBR and long-term performance of intracortical neuroprostheses.
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Affiliation(s)
- Morgan E. Urdaneta
- Department of Neuroscience, University of Florida, Gainesville, FL, United States
| | - Nicolas G. Kunigk
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States
| | - Jesus D. Peñaloza-Aponte
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States
| | - Seth Currlin
- Department of Neuroscience, University of Florida, Gainesville, FL, United States
| | - Ian G. Malone
- Department of Electrical & Computer Engineering, University of Florida, Gainesville, FL, United States
| | - Shelley I. Fried
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
- Boston Veterans Affairs Healthcare System, Boston, MA, United States
| | - Kevin J. Otto
- Department of Neuroscience, University of Florida, Gainesville, FL, United States
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, United States
- Department of Electrical & Computer Engineering, University of Florida, Gainesville, FL, United States
- Department of Materials Science and Engineering, University of Florida, Gainesville, FL, United States
- Department of Neurology, University of Florida, Gainesville, FL, United States
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