Behavioral and Neural Characteristics of Adaptive Speech Motor Control

BEHAVIORAL

Auditory feedback perturbation during speech

The intervention consists of manipulating real-time auditory feedback during speech production. In our lab, such feedback perturbations can be implemented with either a stand-alone digital vocal processor (a device commonly used by singers and the music industry) or with software-based signal processing routines (see Equipment section for details). Note that the study does not investigate the efficacy of these hardware or software methods to induce behavioral change in subjects' speech. Rather, the study addresses basic experimental questions regarding the general role of auditory feedback in the central nervous system's control of articulatory speech movements.

BEHAVIORAL

Visual feedback perturbation during reaching

The intervention consists of manipulating real-time visual feedback during upper limb reaching movements. In our lab, such feedback perturbations can be implemented with a virtual reality display system.

OTHER

DBS stimulation ON/OFF

Patients who have been previously implanted with a DBS stimulator for their clinical care will be tested in two speech motor learning tasks with the stimulation ON and with the stimulation OFF. Note that (1) patients routinely turn the stimulation OFF and back ON (examples are, for some patients, to sleep, to save battery, etc), and (2) we are not in any way evaluating the stimulator itself or its clinical effectiveness but only whether or not two forms of speech motor learning (adaptation to auditory feedback perturbation and speech sequence learning) are affected differently by having the stimulation ON or OFF. implant ON/OFF prior to participation in the speech auditory-motor learning tasks and speech sequence learning tasks. This intervention can be implemented by the subject themselves as all patients have a hand- held controlled that they use to switch stimulation ON/OFF.

Speech formant frequencies

Time frame: Measurements will be made only from acoustic recordings made during the test session (~1 hour).

The frequencies of the subject's first two formants (F1, F2) for each test word will be measured from spectrographic displays with overlaid Linear Predictive Coding formant tracks.

Reach direction for arm movements

Time frame: Outcome measures will be made only during a single data recording session (~2 hours).

Measuring initial reach direction for arm movements allows us to measure the direction that was planned before movement onset.

Amplitude of long-latency auditory evoked potentials (from EEG recordings) responses

Time frame: Measurements will be made only from electroencephalography (EEG) recordings made during the test session (~2 hours).

Amplitude of the N1 component (in microvolt) will be measured in response to both probe tones and to a subject's own speech onset.

Local field potentials recorded by neural implants

Time frame: Measurements will be made only from DBS implant recordings made during the test session (~1-2 hours).

Local field potentials (LFPs) will be recorded by the PerceptPC DBS implants and used to measure changes in power spectrum density across different phases of the tasks. Additionally, LFPs will be used to conduct event-related analyses.

Temporal measures of speech syllable sequence learning

Time frame: Outcome measures will be made only during a single data recording session (~0.5 hours)

1\. Speech onset time (in milliseconds); 2. Average syllable duration (in milliseconds)

Accuracy during speech syllable sequence learning

Time frame: Outcome measures will be made only during a single data recording session (~0.5 hours)

Sequence accuracy (in percent)

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