All animals with a spine have a brain, as do most animals without a spine, with the exception of sponges, jellyfish and starfish. The brain is the center of the body’s nervous system, which specializes in signal processing and coordination. Together with the spine the brain is made up of nerve cells (neurons) that transmit electrical and chemical signals. Some neurons respond to touch, sound or light, others to muscle contractions and glands. The brain has evolved differently in different species. The human brain can roughly be divided into three parts: the cerebrum, the cerebellum at the lower back of the head, and the brainstem that joins the brain to the spinal cord. The cerebrum controls voluntary movement of the body, sensory processing, speech, language and memory. The cerebellum is involved in fine-tuned motor control. While the human brain contributes to about 2% of the total body weight, it consumes about 20% of the energy, or twice as much as the heart (Elia, 1992). When the brain is busy it produces spontaneous electrical activity along the scalp, based on ionic current flows within the neurons of the brain (Niedermeyer & Lopes da Silva, 2004). The brain is always busy unless you are dead.
EEG
Electroencephalography (EEG) is a technique used to record the brain’s electrical activity, mainly in the outermost sheet of the cerebrum called the cerebral cortex, by placing conducting metal electrodes along the scalp. EEG has a long history in clinical, biological and psychological research, dating back to the work of Caton (1875) and Berger (1924). For example, an EEG study by Hobson & McCarley (1977) showed that dreaming is an automatic neural mechanism (perhaps simply to keep the brain occupied) and not, as Freud (1913) suggested, a manifestation of our deepest desires and secrets.
3.1 EEG wireless headset
Researchers from Imec (Interuniversity Microelectronics Centre) and Holst Centre have developed a wireless, low-power EEG headset with the aim to improve patients’ quality of life (Gyselinckx et al., 2005). This is called a brain-computer interface (BCI). In comparison to commercial devices such as EPOC14, the IMEC/Holst prototype focuses on low power consumption and long- term use (Patki, Grundlehner, Nakada & Penders, 2011). For example, in the case of epilepsy, abnormal neuronal activity can be observed using EEG analysis (Fisher et al., 2005). Ambulatory monitoring allows epileptics patients to be tracked while continuing their daily activities.
ALPHA, BETA & DELTA WAVES
The headset consists of a microprocessor, a wireless communication module and dry electrodes located at specific positions on the head to capture EEG signals. Different signals are captured at different positions. For example, alpha waves are neural oscillations that primarily occur in the occipital lobe at the back of the brain, during wakeful relaxation with closed eyes. Other well- known oscillations include beta waves (waking consciousness) and delta waves (deep sleep). 14http://emotiv.com/
3.2 EEG affective visualization
VALENCE (De Smedt & Menschaert, 2012) is a generative art installation created in NODEBOX FOR OPENGL. It presents an interactive game based on brain activity recording. Traditionally,
computer games respond to the player’s interaction with a game controller such as a joystick or a gamepad. But there are other physiological (e.g., heart rate) and behavioral (e.g., gesture, posture, facial expression) indicators of the player’s emotional state (Gilleade, Dix & Allanson, 2005). Monitoring such affective biofeedback (Bersak et al., 2001) can be useful to improve the gaming experience. With the introduction of immersive technology, the highly competitive games industry has changed substantially in a short amount of time (Sung, 2011). For example, with the Nintendo Wiimote controller, the body of the player replaces the traditional console. With the Xbox Kinect motion sensing system, the physical space around the player is transformed into a game world. Such devices have in turn been adopted by the scientific and artistic communities. For example, Gallo, De Pietro & Marra. (2008) use the Wiimote as a 3D user interface for physicians to investigate patients’ anatomy. In the arts, Jordà, Geiger, Alonso & Kaltenbrunner (2007) used motion sensing to create the REACTABLE, a collaborative electronic music instrument.
In our work, we use the Imec/Holst headset to control a physics-based simulation. When the player wearing the headset relaxes, the virtual world responds by constructing an aesthetically pleasing composition. We focus on alpha waves (relaxation) and the valence hypothesis (arousal).
VALENCE
The valence hypothesis states that the right brain hemisphere is dominant for negative or unpleasant emotions, and that the left hemisphere is dominant for positive or pleasant emotions. Research in this area has been conducted by Penders, Grundlehner, Vullers & Gyselinckx (2009). We monitor the readings of two electrodes to control the simulation, one left and one right on the back of the head. Since readings can be prone to fluctuation (e.g., a sudden high or low peak) we use a simple moving average (SMA) on the data. The SMA is calculated by taking the average of progressive subsets of the data, smoothing short-term fluctuations and highlighting long-term trends. The hardware setup is illustrated in figure 16.
Figure 16. Hardware setup. Laptop 1 analyzes the EEG readings from the wireless headset and sends the SMA values to laptop 2, which renders the visualization using NODEBOX FOR OPENGL.