Increased Event-Related Potentials and Alpha-, Beta-, and Gamma-Activity Associated with Intentional Actions

Abstract

Objective: Internally guided actions are defined as being purposeful, self-generated and offering choices between alternatives. Intentional actions are essential to reach individual goals. In previous empirical studies, internally guided actions were predominantly related to functional responses in frontal and parietal areas. The aim of the present study was to distinguish event-related potentials and oscillatory responses of intentional actions and externally guided actions. In addition, we compared neurobiological findings of the decision which action to perform with those referring to the decision whether or not to perform an action.

Methods: Twenty-eight subjects participated in adapted go/nogo paradigms, including a voluntary selection condition allowing participants to (1) freely decide whether to press the response button or (2) to decide whether they wanted to press the response button with the right index finger or the left index finger.

Results: The reaction times were increased when participants freely decided whether and how they wanted to respond compared to the go condition. Intentional processes were associated with a fronto-centrally located N2 and P3 potential. N2 and P3 amplitudes were increased during intentional actions compared to instructed responses (go). In addition, increased activity in the alpha-, beta- and gamma-frequency range was shown during voluntary behavior rather than during externally guided responses.

Conclusion: These results may indicate that an additional cognitive process is needed for intentional actions compared to instructed behavior. However, the neural responses were comparatively independent of the kind of decision that was made (1) decision which action to perform; (2) decision whether or not to perform an action).

Significance: The study demonstrates the importance of fronto-central alpha-, beta-, and gamma oscillations for voluntary behavior.

Keywords: EEG; event-related potentials; intentional action; oscillatory activity; voluntary selection.

FIGURE 1

Paradigm: sinusoidal tones of three differential pitches were presented (duration: 50 ms, pressure level: 100 dB). The tones were presented in pairs at intervals of 1000 ms. The interval between trials lasted 2000 ms. The go condition comprised the combination of the middle-frequency tone (tone b: 1000 Hz; cue stimulus) followed by the high-frequency tone (tone c: 1300 Hz). In the nogo task, the cue stimulus was followed by a low-frequency tone (tone a: 800 Hz). In the voluntary selection condition, the cue stimulus was followed by the tone with a same frequency. The go condition was presented 160 times, nogo, and voluntary selection were presented 80 times.

FIGURE 2

Auditory evoked potentials of healthy controls. (A) ERPs concerning the paradigm +/-; (B) ERP results regarding the paradigm R/L. Subjects showed increased fronto-centrally located N2 amplitudes during the voluntary selection task and nogo condition compared to go. The P3 amplitude was located in fronto-central brain areas during the nogo condition and the voluntary selection condition. Abbreviations μV, microvolt; ms, milliseconds.

FIGURE 3

Comparison of the voluntary selection-related responses during paradigm +/- and paradigm R/L. The ERP results differed only marginally between paradigms. Abbreviations μV, microvolt; ms, milliseconds.

FIGURE 4

Time frequency analyses. Comparison of alpha-, beta-, and gamma-power during go, nogo, and voluntary selection in Cz. Activity was increased during voluntary selection compared to go and nogo condition. ms, milliseconds.