During Fastball, stimuli are rapidly and sequentially presented to participants. The brain generates a signal called the steady-state evoked potential (SSEP), which occurs at the same frequency as the stimuli presentation.
If a stimulus in this sequence differs from the others, an additional brain response should occur, in response to these differing stimuli. Therefore, if participants can differentiate between the two types of stimuli, we should observe two separate types of brain activity in the EEG signal, one that relates to the general stimuli presentation and one relating to the differing stimuli.
By manipulating the type of stimuli we present and how certain stimuli differ from the norm, it is possible to investigate different cognitive functions using Fastball. For example, a task that requires participants to differentiate between two semantic categories (e.g., birds and mammals), could be used to assess semantic categorisation. Alternatively, a task requiring participants to differentiate between objects and abstract shapes could assess objection perception.
These will be tested in healthy adults and compared to existing neuropsychological measures, with the eventual aim of the Fastball tasks being used as a diagnostic tool for dementia.