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Final goal : Graphic interface to mind based on subconsciousnes generated visul data showed in visual field ( mind eye ).
field. By analogy, unstructured or de-structured stimulation can be applied to other sensory systems, e.g., auditory or tactile. Studies aiming at induction of ASC have been using ‘multi-modal ganzfeld’ (MMGF), i.e., simultaneous exposure to unstructured visual and auditory input.
ground differentiation in the ganzfeld and colour perception (see Avant, 1965, for a review, cf. also Tsuji et al., 2004).
2002; Pu¨ tz et al., 2006) a red-coloured incandescent 60-W lamp, placed at a distancew120 cm from the eye-shields, was used as the light source; in recent studies, where a precise control of the ganzfeld colour is important, a computerdriven, xenon lamp based D-ILA projector has been used (Pu¨ tz and Wackermann, 2007). The choice of red colour reportedly (Cohen, 1958) facilitates the observers’ ‘immersion’ in the ganzfeld.
already after a relatively short exposure to the visual or MMGF (a few minutes). The visual field’s luminance diminishes and the field shows diffuse inhomogeneities, often described as a ‘cloudy fog’. In case of a colour ganzfeld, the field’s colour gradually bleaches, up to the point of a loss of the sensation of colour: the field is of indefinite grey, sometimes with an undertone of the complementary colour, e.g., greyish-green if red light is used. In addition, more distinct structures may appear against the diffuse ‘foggy’ background: dots, zig-zag lines, or more complex patterns. Generally, these elementary perceptual phenomena can be accounted for by adaptive retinal processes: saturation of the receptive elements and their mutually inhibitory interactions
minutes) to the ganzfeld, some subjects report complex percepts
ganzfeld are episodes of ‘‘complete disappearance of the sense of vision for short periods of time’’, also called ‘blankouts’ (Cohen, 1960), occurring after prolonged exposure (10– 20 min) to the ganzfeld. Subjects also report that during these periods they were uncertain whether their eyes were open or closed, or even unable to control their eye movements. In the ‘luminous fog’ of the ganzfeld the subjects do not see anything; in the ‘blank-out’ periods, they may experience presence of ‘nothingness’ (Gibson, 1979).
three reported above emerged after a ‘blank-out’ period. Herrmann (2001) in an electroencephalographic (EEG) study of the visual cortex’s response to a flickering visual field observed the appearance of subjective colours and forms. Herrmann and Elliott (2001) described the variety of these perceptual phenomena as a function of flicker frequency (1– 40 Hz). Recently, Becker and Elliott (2006) reported cooccurrences of forms and colours in a flickering ganzfeld being dependent on flicker frequency, and phase relationship between the subject’s response and the flicker period.
The image created by the eye’s optical system can be fixed on the retina by special techniques (Heckenmueller, 1965). The structure of the visual field thus remains preserved but the scanning motion due to eye movements is inhibited. Under these conditions, partial or total ‘fade-outs’ of the visual field may occur (Yarbus, 1967), indicating that a regular refreshing is necessary for maintaining the visual structure. We may hypothesise a relationship between these ‘fade-outs’ and the ‘blank-out’ periods in ganzfeld, where eye movements are reportedly reduced.
revealed functional differences between sub-bands within the alpha frequency range: low-frequency alpha, reflecting rather attentional processes, and high-frequency alpha reflecting cognitive processes (Klimesch, 1997, 1999; cf. also Shaw, 2003).
higher alpha activity in the resting EEG and individual susceptibility to ‘blank-outs’. Cohen (1960) interpreted occurrence of alpha activity during the ‘blank-outs’ as alpha rebounddthis is a well-known phenomenon where, after a transitory suppression e.g., due to an external stimulus, eyes opening, etc., alpha activity attains the original level, or even increases. Tepas (1962) found an increase of alpha amplitude during the ‘blank-outs’, which was intermediate to ‘eyes closed’ and ‘eyes open’ conditions, but could not confirm the hypothesised relation between high alpha activity and blank-out susceptibility. These findings are in line with early observations by Adrian and Matthews (1934), who had previously reported alpha rebound after eyes opening in a uniform visual field. Later, Lehtonen and Lehtinen (1972) also reported re-occurrence of alpha activity in the ganzfeld, comparable to the ‘eyes closed’ condition. Increase of alpha activity was also observed during the ‘fade-out’ periods in perception of stabilised retinal images (Lehmann et al., 1967); this supports the relation to ganzfeld ‘blank-outs’ hypothesised above. As shown in the preceding sections, the variety of ganzfeld- induced phenomena is fairly rich and suggests relations to several different classes of perceptual phenomena and/or states of consciousness. Objective characterisation of the brain’s functional states under ganzfeld stimulation by means of EEG measures may help to elucidate these relations. This was the objective of our two major ganzfeld studies, results of which are summarised below.
that eyes-open and eyes-closed conditions are not equivalent even in the absence of any visual input (Marx et al., 2003).
waking states were best distinguished by the band power ratio a2/a1 (frequency ranges 10–12 Hz and 8–10 Hz, respectively), which was increased in the ganzfeld EEG, indicating an acceleration of the alpha activity. Visual inspection of the spectra reveals a power drop along the lower flank of the alpha peak in the ganzfeld EEG, leading to an increase of the peak frequency
the time segment 20–10 sec before the report. A time–frequency analysis of the data gave additional evidence for alpha acceleration (Wackermann et al., 2003).
profiles’ over the analysed 30 sec time window. The most stable correlation over this time window was a global (i.e., involving all 19 channels) negative correlation between a2 power, measured relative to individual GFB baselines, and subject-reported vividness of imagery.
was interpreted by Pu¨ tz et al. (2006) as an indicator of activation of thalamo-cortical feedback loops involved in retrieval, activation and embedding of memory content in the ganzfeld-induced imagery. The observed a1 attenuation during the analysis epoch may reflect a shift of attention towards the visual percept and, later, preparation of the required motor action (button press signalling occurrence of imagery). The unspecific alpha-inducing effect of the ganzfeld-induced steady-state (no imagery) is in line with the inhibition hypothesis (i.e., alpha synchronisation due to inhibition of cortical areas related to external sensory information processing), and with earlier findings of other authors mentioned above
this chnage is noticable in relaxation but is hard to describe it its like change from 2D to 3D balacknes diffent preception of space .This change have different levels i suspect it depends how much senses is turn off (vision , proprioreception..)