Core Semantic Systems TMS (CSST)

Core Semantic Systems of the Human Brain

This study examines the time course of activation of the left anterior temporal lobe (ATL) during lexical processing using Transcranial Magnetic Stimulation (TMS).

Study Overview

• Status: Recruiting
• Conditions: Lexical Access in Neurotypicals
• Intervention / Treatment: Device: Single-pulse TMS

Detailed Description

This study investigates the activation time of the anterior temporal lobe (ATL) region during lexical processing. Participants will perform three tasks: lexical decision, semantic decision (divided into noun and verb semantic decision), and number judgment.

Lexical Decision Task: Participants will be shown words and pseudowords (e.g., excaid). Participants have to decide if the presented stimulus is a real word or a pseudoword.

Semantic Decision Task: Participants will determine if the stimulus word refers to an action or an object that can be manipulated using the hand or arm.

Half of the stimuli will be nouns, constituting the first semantic decision task with objects, and the other half will be verbs, constituting the second semantic decision task with actions.

Number Judgment Task: Participants will decide if a presented number was divisible by four (e.g., 64) or not (e.g., 69). The stimuli will include numbers with either two or three digits.

For each task, we will collect accuracy and reaction time (RT) data. The primary analyses concern the RTs, but accuracies will also be examined in secondary analyses.

A single pulse TMS will be applied at three different time points: -100 ms, 150 ms, and 400 ms after the onset of the stimulus item. A Magstim BiStim² stimulator with a figure-8 coil will be used. The resting motor threshold (RMT) will be defined as the minimum intensity required to stimulate the motor cortex, eliciting a contraction of the abductor pollicis brevis in at least 5 out of 10 trials. The coil will be positioned at a 45-degree angle along the parasagittal line on the presumed motor cortex area for the APB muscle and adjusted in different directions to find the optimal motor hotspot. Intensity will be between 100% and 120% of resting motor threshold as tolerated by the participant.

The effect of TMS on the response time (RT) at different time points will be examined. TMS will be applied at the left anterior middle temporal gyrus at 10 mm posterior to the tip of the temporal pole. A structural MRI scan will be collected prior to the TMS, which will be used in localizing The target spot. A BrainSight neuronavigation system will be used, with the MRI scan collected before, to localize the target location on the scalp. The tasks will last approximately 30 minutes.

• Study Type: Interventional
• Enrollment (Estimated): 36
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Rutvik H Desai, PhD; Phone Number: 8032617149; Email: rutvik@sc.edu

Study Locations

• United States
  • South Carolina
    • Columbia, South Carolina, United States, 29208
      • Recruiting
      • Prisma Health Richland
      • Contact: Rutvik H Desai, PhD; Phone Number: 803-261-7149; Email: rutvik@sc.edu
      • Principal Investigator: Rutvik H Desai, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Participants must be within the ages of 18 to 40
• Native speakers of English

Exclusion Criteria:

• Potential participants with a clinically reported history of dementia, alcohol abuse, psychiatric or neurological disorders, traumatic brain injury, or extensive vision or hearing problems that prevents them from performing the tasks
• Contraindication to TMS, determined by a standard TMS screening form
• Contraindication to MRI, determined by a standard MRI screening form
• Left handed participants

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: TMS	Device: Single-pulse TMS; A single pulse TMS is delivered at different time points when processing words or numbers.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean reaction time changes in lexical decision from TMS at 150 ms	An interaction between time point (-100, 150) and task (lexical decision, number judgment) RT at the group level (one tailed). (LD_150 - LD_-100) - (NJ_150 - NJ_-100).	Through study completion, an average of 1 year.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean reaction time changes in semantic decision from TMS at 150 ms	An interaction between time point (-100, 150) and task (semantic decision, number judgment) RT at the group level (one tailed). (SD_150 - SD_-100) - (NJ_150 - NJ_-100).	Through study completion, an average of 1 year.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean reaction time changes in lexical decision from TMS	LD RT at -100 ms will be lower than LD RT at 150 ms.	Through study completion, an average of 1 year.
Mean reaction time changes in semantic decision from TMS	Sematic decision RT at -100 will be lower than RT at 150 ms.	Through study completion, an average of 1 year.
Mean reaction time changes in lexical decision from TMS at 400 ms	An interaction between time point (-100, 400) and task (lexical decision, number judgment) RT at the group level (one tailed). (LD_400 - LD_-100) - (NJ_400 - NJ_-100).	Through study completion, an average of 1 year.
Mean reaction time changes in semantic decision from TMS at 400 ms	An interaction between time point (-100, 400) and task (semantic decision, number judgment) RT at the group level (one tailed). These effects will be examined separately for nouns and verbs as well. (SD_400 - SD_-100) - (NJ_400 - NJ_-100).	Through study completion, an average of 1 year.
Mean reaction time changes in noun semantic decision from TMS at 150 ms	An interaction between time point (-100, 150) and task (semantic decision of nouns, number judgment) RT at the group level (one tailed). (SD_noun_150 - SD_noun_-100) - (NJ_150 - NJ_-100).	Through study completion, an average of 1 year.
Mean reaction time changes in verb semantic decision from TMS at 150 ms	An interaction between time point (-100, 150) and task (semantic decision of verbs, number judgment) RT at the group level (one tailed). (SD_verb_150 - SD_verb_-100) - (NJ_150 - NJ_-100).	Through study completion, an average of 1 year.

Collaborators and Investigators

• Sponsor: University of South Carolina
• Collaborators: National Institute on Deafness and Other Communication Disorders (NIDCD)

Study record dates

Study Major Dates

• Study Start (Actual): April 23, 2024
• Primary Completion (Estimated): August 1, 2025
• Study Completion (Estimated): September 1, 2025

Study Registration Dates

• First Submitted: September 23, 2024
• First Submitted That Met QC Criteria: March 5, 2025
• First Posted (Actual): March 25, 2025

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: March 5, 2025
• Last Verified: March 1, 2025

More Information

Terms related to this study

• Keywords: time course; semantic processing; lexical access; anterior temporal lobe
• Other Study ID Numbers: Pro00098791; R01DC017162 (U.S. NIH Grant/Contract)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No