Clinical trial NCT06870552: Core Semantic Systems TMS
Official title: Core Semantic Systems of the Human Brain
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: NA
Conditions: Lexical Access in Neurotypicals
Keywords: semantic processing
time course
lexical access
anterior temporal lobe
Lead sponsor: University of South Carolina
Sponsor class: OTHER
Collaborators: name: National Institute on Deafness and Other Communication Disorders (NIDCD)
First posted: 2025-03-11
Enrollment: 36
Sex: ALL
Minimum age (years): 18
Maximum age (years): 40
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: NA
Intervention model: SINGLE_GROUP
Primary purpose: BASIC_SCIENCE

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

Eligibility criteria: 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

Primary outcomes:
measure: Mean reaction time changes in lexical decision from TMS at 150 ms
timeFrame: Through study completion, an average of 1 year.
Secondary outcomes:
measure: Mean reaction time changes in semantic decision from TMS at 150 ms
timeFrame: Through study completion, an average of 1 year.
Other outcomes:
measure: Mean reaction time changes in lexical decision from TMS
timeFrame: Through study completion, an average of 1 year.
measure: Mean reaction time changes in semantic decision from TMS
timeFrame: Through study completion, an average of 1 year.
measure: Mean reaction time changes in lexical decision from TMS at 400 ms
timeFrame: Through study completion, an average of 1 year.
measure: Mean reaction time changes in semantic decision from TMS at 400 ms
timeFrame: Through study completion, an average of 1 year.
measure: Mean reaction time changes in noun semantic decision from TMS at 150 ms
timeFrame: Through study completion, an average of 1 year.
measure: Mean reaction time changes in verb semantic decision from TMS at 150 ms
timeFrame: Through study completion, an average of 1 year.
Locations:
city: Columbia
country: United States
facility: Prisma Health Richland
state: South Carolina
Study officials:
References: