sometimes appear to be more a continuum of states than a set of discrete percepts. For example, in TMS of cortex, single-anddouble-wedge (bow-tie/butterfly) phosphenes are common. Kammer et al. (2005) found that single wedges are seen at lowerstimulus intensities and that butterfly wedges extend into bothvisual fields at higher intensities. These also occur in epilepsy(Babb, Halgren, Wilson, Engel, & Crandall, 1981), but a morecommon form for occipital epilepsy is a doughnut-shaped pho-sphene. This favoritism for certain forms recalls Kenet et al. 's(2003) finding that some spontaneously formed cortical activitypatterns occur more frequently than others. It is also interestingto note that these particular phosphenes would correspond tosingle vertical or horizontal stripes of cortical activation (adouble wedge results if a horizontal stripe forms symmetricallyon both occipital cortices). The length and position on cortex ofthese stripes would determine the size and location of thephosphene. Since isolated stripes could occur early in thepattern-formation process and could wane before seeding a fullperiodic pattern, this could provide a route to understandingsuch phosphenes. Alternately, some pattern-forming systemscan form single stripes as a final state (known as a bump inneural field theory; see Kishimoto & Amari, 1979; see also Coombes, 2005; Ermentrout & Terman, 2010). Similarly, thesmall rotating pinwheels and spoked stars seen in some elec-trical stimulations of cortex (Dobelle & Mladejovsky, 1974;Penfield & Rasmussen, 1950) could be small Klu ¨ver patterns created by Ermentrout-Cowan mechanisms but could also rep-resent a small wave front of excitation, activating in sequenceorientation-specific cell populations as the wave moves througha single orientation column (Schwartz, 1980), similar to amechanism sometimes evoked to explain migraine scintillation. Eye Movements, Edge-Sharpening Mechanisms, and Hallucination In ordinary vision, the visual system compensates for eye move-ments in various ways, perceptually stabilizing the moving world,deblurring image motion for some eye movements, and blockingvisual perception during fast saccades and blinks (Volkmann,1986). Similar phenomena can be found in visual hallucinations,but the overall picture is incomplete because these phenomena aremostly the subject of observer commentary rather than systematicstudy. Clearly, dream imagery is compatible with rapid eye move-ments, as is eidetic imagery, and neither seems to shift with eyemovements (Gru ¨sser & Landis, 1991). However, migraine hallu-cinations and experimentally induced phosphenes all shift in thedirection of gaze for saccadic and pursuit eye movements (Gru ¨sser, 1986). The differences may lie in whether the cortical area inwhich the hallucination arises is directly involved in corollary-discharge-based eye movement compensation. Evidence for addi-tional postprocessing exists. For example, in CBS, clinical visualloss leads to sensory deprivation hallucinations that can sometimesbe abolished by making saccadic (but not pursuit) eye movements(Kölmel, 1985), especially for saccades toward the normal portionof the visual field (Vaphiades, Celesia, & Brigell, 1996). This joinsfindings that saccades disrupt not only active vision but visualphosphenes (Riggs, Merton, & Morton, 1974) and visual cognitiondriven by mental imagery (Brockmole, Carlson, & Irwin, 2002). Curiously, when Charles Bonnet hallucinations originate in nowblind areas of peripheral visual field, they seem sharper than is normally seen in periphery. Similarly, Richards (1971) noted thatconverging eye movements can make migraine hallucinationsseem sharper than otherwise. In both cases, the anomalous sharp-ening is similar to the neural deblurring that occurs for someviewing conditions (e. g., Hammett & Bex, 1996). Pattern Formation in Other Sensory Cortices: What Would Cortical Stripes Sound Like? The cytoarchitecture of visual cortex is replicated in other sensory cortices; pattern formation is likely to occur in othersensory cortices and should be experienced in characteristicways as auditory, somatosensory, or other hallucinations. Forexample, an unfortunate somatosensory hallucination that canoccur in migraine is formication, a sensation of insects movingon or under the skin. This might be explained as the analogueof a visual fortification arc; a scintillating fortification wavefront moving through somatosensory cortex could result in asensation of spreading irregular movement across a section ofskin. Similarly, Klu ¨ver (1966) described a curious synesthesia experienced by a mescaline-dosed subject who reported notonly seeing hexagonal textures (which he called fretwork) butalso that he himself seemed to be made of the same pattern. Another subject could feel a moving cobweb sensation on histongue. A third subject reported that his legs and feet becamerotating spirals, identical to the rotating spiral he was seeing inhis visual field, and that he could feel them as rotating spirals;“one has the sensation of somatic and optic unity” (p. 71). Several of these reports came from physicians and show usefulinsights but might carry little weight if not for similar reports ofgeometric percepts in somatosensory synesthesia without intox-ication (Cytowic, 1989). Some of Klu ¨ver's reports are sugges-tive of sensory binding between visual and somatosensorycortex. There is precedent for this: Tactile two-point discrimi-nation on a limb improves if the limb is viewed under magni-fication, even if the magnified view is uninformative, suggest-ing that visual magnification forces some kind of slavedmagnified remapping of somatosensory cortex (Jackson, 2001;Kennett, Taylor-Clarke, & Haggard, 2001). Moreover, entrain-ment of pattern formation between cortices does not requiremassive coupling; in simulations intended to probe the conti-nuity of visual hallucinations between the two visual hemi-spheres, Rule et al. (2011) found that only a thin band ofsimulated connecting neurons was enough to cause identicalstripe formation in the two cortices. This begs the question, Ifpattern formation occurs in nonvisual cortex (and given thestructural similarities between sensory cortices, it is likely),would the orientation of the stripes be as perceptually mean-ingful as they are in visual cortex? To answer this may requirethat the work that illuminated visual hallucinations in visualcortex be recapitulated for the other senses and their associatedcortices. Such an effort would have three main thrusts: First,like Klu ¨ver, we need to synthesize reports of nonvisual hallu-cinations in synesthesia, migraine, epileptic seizures, and otherinducing conditions, seeking recurrent archetyped nonvisualhallucinations that are analogues of Klu ¨ver's visual form con-stants. Some of these may correspond to stripe patterns onspecific sensory cortices, as Klu ¨ver's visual forms did. Second,765 HALLUCINATIONS AND CORTICAL PATTERN FORMATION