Karim Johari Picture

Karim Johari

Assistant Professor

86 Hatcher Hall

Email Address:

Office Phone:


Humanities & Social Sciences

Communication Sciences & Disorders


Ph.D. Communication Sciences and Disorders, University of South Carolina (2019)

M.Sc. Speech Therapy, Tehran University of Medical Sciences (2011)

B.Sc. Speech Therapy, Iran University of Medical Sciences (2008)


Human Neurophysiology and Neuromodulation Lab.



Current Research

Karim Johari is an assistant professor in the department of communication sciences and disorders. He directs Human Neurophysiology and Neuromodulation Lab. He utilizes invasive ( ECog ), non-invasive neurophysiology (EEG), HD-tDCS/tACS and computational modeling to investigate neural correlates of speech production  and limb movement,  and the interaction between the motor system and language ( motor-language coupling). The current projects in his lab are the validation of HD-tACS for improvement of speech and limb motor control in healthy older adults and individuals with neurodegenerative conditions such as Parkinson’s disease.

Research Interests

  • Neural Correlates of Speech and Limb Motor Control
  • Normal Aging Effects on Speech and Limb Motor Control
  • Speech and Language Impairments in Parkinson’s Disease
  • Invasive (LFPs) and Noninvasive Electrophysiology (EEG)
  • High-Definition Transcranial Direct/Alternating Current Stimulation (HD-tD/ACS)
  • Machine Learning and Computational Modeling                                                       


  1. Tabari F, Parton C, Cryer H & Johari, K. HD-tDCS Over Left Supplementary Motor Area Differentially Modulated Neural Correlates of Motor Planning for Speech vs. Limb Movement. International Journal of Psychophysiology (2024).
  2. Tabari F, Berger J, Flouty O, Copeland B, Greenlee J, & Johari K. Speech, Voice, and Language Outcomes Following Deep Brain Stimulation in Parkinson’s Disease and Essential Tremors: A Systematic Review of Literature. Plos One (2024).
  3. Johari K, Berger JI. Theta oscillations within right dorsolateral prefrontal cortex contribute differently to speech versus limb inhibition. Journal of Neuroscience Research (2024).
  4. Johari K, Berger J. High-Definition Transcranial Direct Current Stimulation Over Right Dorsolateral Prefrontal Cortex Differentially Modulates Inhibitory Mechanisms for Speech vs. Limb Movement . Psychophysiology (2023). 
  5. Johari K, Kelley R, Tjaden K, Patterson C, Rohl A, Berger J, Corcos D& Greenlee J. Subthalamic Nucleus Neurons Differentially Encode Speech and Limb Movement in Parkinson's Disease. Frontiers in Human Neuroscience (2023). 
  6. Johari K, Tabari F& Desai, R. Right Frontal HD-tDCS Reveals Causal Involvement of Time perception Networks in Temporal Processing of Concepts. Scientific Reports (2023).
  7. Desai R.H, Hackett T, Lai V, Riccardi N& Johari K. Spatiotemporal Characteristics of the Neural Representation of Event Concepts. Brain&Language (2023).
  8. Johari K, Lai V, Riccardi N&Desai R. Temporal Features of Concepts Are Grounded in the Time Perception Neural Networks:An EEG study. Brain&Language (2023).
  9. Shaheen N, Shaheen A, Sarica C, Singh A, Zanaty M, Johari K, Yang A, Zesiewicz T, Dalm B, Bezchlibnyk Y, Lozano A & Flouty O. Deep brain stimulation for substance use disorder: a systematic review and meta-analysis.  Frontiers in Psychiatry (2023)
  10. Berger J, Johari K, Kovach C & Greenlee J. Speech Artifact is also Present in Spike Data.  Neuroimage (2022).
  11. Johari K, Riccardi N, Malyutina S, Modi M & Desai R. HD-tDCS of Primary and Higher-order Motor Cortex Affects Action Word Processing. Frontiers in Human Neuroscience (2022).
  12. Rohl A, Gutierrez S, Johari K, Greenlee J, Tjaden K, Roberts A. Speech dysfunction, cognition, and Parkinson's disease. Progress in Brain Research (2022).
  13. Kopf L, Rohl A, Nagao T, Bryant K, Johari K, Tjaden K, Greenlee J. Voice Handicap Index in Parkinson’s patients: Subthalamic versus Globus Pallidus Deep Brain Stimulation. Journal of Clinical Neuroscience (2022).
  14. Johari K, Behroozmand R. Neural Correlates of Speech and Upper Limb Motor Timing Deficits Revealed by Aberrant Beta Band Desynchronizations in Parkinson’s Disease. Clinical Neurophysiology (2021).
  15. Johari K, Riccardi N, Malyutina S, Modi M, Desai R. HD-tDCS over Motor Cortex Facilitates Action Sentence Processing. Neuropsychologia (2021).
  16. Gill A, Johari K, Fitzpatrick M, Thompson E, den Ouden D, Behroozmand R. Improving Speech and Upper Limb Motor Reaction Times through High-definition transcranial Direct Current Stimulation of the Left Ventral Motor Cortex. Brain Stimulation (2021).
  17. Johari K, Behroozmand R. Event-related Desynchronization of Alpha and Beta Band Neural Oscillations Predict Speech and Limb Motor Timing Deficits in Normal Aging. Behavioural Brain Research (2020).
  18. Behroozmand R, Johari K, Bridwell K, Hayden C, Fahey D, den Ouden DB. Modulation of Vocal Pitch Control through High-Definition Transcranial Direct Current Stimulation of the Left Ventral Motor Cortex. Experimental Brain Research (2020).
  19. Phillip Johnson L, Sangtian S, Johari K, Behroozmand R, Fridriksson J. Slowed Compensation Responses to Altered Auditory Feedback in Post-Stroke Aphasia: Implications for Speech Sensorimotor Integration. Journal of Communication Disorders (2020).
  20. Reifegerste J, Estabrooke I.V, Russell L.E, Veríssimo J, Johari, K, Wilmarth B, Pagan F.L, Moussa C and Ullman. Can Sex Influence the Neurocognition of Language? Evidence from Parkinson's Disease. Neuropsychologia(2020).
  21. Behroozmand R, Johari K, Kelley R, Kapnoula E, Narayanan N, Greenlee J. Effect of Deep Brain Stimulation on Vocal Motor Control Mechanisms in Parkinson’s Disease.
  22. Parkinsonism & Related Disorders (2019). 
    Behroozmand R, Johari K. Pathological Attenuation of the Right Prefrontal Cortex Activity Predicts Speech and Limb Motor Timing Disorder in Parkinson’s Disease. Behavioural Brain Research (2019): Equally Contributed.
  23. Johari K, den Ouden DB, Behroozmand R. Behavioral and Neural Correlates of Normal Aging Effects on Motor Preparatory Mechanisms of Speech Production and Limb Movement. Experimental Brain Research (2019).  
  24. Johari K, Walenski M, Reifegerste J, Ashrafi F & Ullman M.T.Sex, Dopamine, and Hypokinesia: A Study of Inflectional Morphology in Parkinson’s disease. Neuropsychology (2019).
  25. Johari K, Walenski M, Reifegerste J, Ashrafi F, Behroozmand R, Daemi M, Ullman MT. A Dissociation between Syntactic and Lexical Processing in Parkinson’s Disease. Journal of Neurolinguistics (2019).  
  26. Behroozmand R, Phillip L, Johari K, Bonilha L, Rorden C, Hickok G, Fridriksson J. Sensorimotor Impairment of Speech Auditory Feedback Processing in Aphasia. Neuroimage (2018).
  27. Behroozmand R, Johari K. Sensorimotor Impairment of Speech and Hand Movement Timing Processing in Parkinson’s Disease. Journal of Motor Behavior (2018): Equally Contributed.
  28. Johari K, Behroozmand R. Functional Dissociation of Temporal Processing Mechanisms during Speech Production and Hand Movement: An ERP Study. Behavioural Brain Research (2018).
  29. Johari K, den Ouden DB, Behroozmand R. Effects of Aging on Temporal Predictive Mechanisms of Speech and Hand Motor Reaction Time. Aging Clinical and Experimental Research (2018).  
  30. Johari K, Behroozmand R. Premotor Neural Correlates of Predictive Motor Timing for Speech Production and Hand Movement: Evidence for a Temporal Predictive Code in the Motor System. Experimental Brain Research (2017).  
  31. Johari K, Behroozmand R. Temporal Predictive Mechanisms Modulate Motor Reaction Time during Initiation and Inhibition of Speech and Hand Movement. Human Movement Science (2017).
  32. Johari K, Ashrafi F, Zali A, Ashayeri H, Fabbro F, & Zanini S. Grammatical Deficits in Bilingual Azari – Farsi Patients with Parkinson's Disease. Journal of Neurolinguistics (2013).  
  33. Ashrafi F, Mohammadhassanzadeh H , Shokraneh F, Valinejadi A, Johari K & Saemi N. Iranians’ Contribution to World Literature on Neuroscience. Health Information & Libraries Journal (2012).  
  34. Ashrafi F, Zali A, Pakdaman H & Johari K. Cognitive Impairments in Parkinson’s Disease: Evidence from Iranian’s Population. Iranian Journal of Neurology (2012).  
  35. Johari, K & Ashayeri H. The Grammatical Deficit in Regular Past Tense Formation: Study of Persian Speaking Population with Parkinson Disease. Stem-, Spraak- en Taalpathologi (2012).