Deep dyslexia is right-hemisphere reading

Two views exist concerning the proper interpretation of the form of acquired dyslexia known as deep dyslexia: (a) that it represents reading by a multiply damaged left hemisphere reading system; (b) that it represents reading which relies extensively on right-hemisphere orthographic and semantic processing. Price, Howard, Patterson, Warburton, Friston, and Frackowiak (1998) have recently reported a brain-imaging study whose results, they claim, "preclude an explanation of deep dyslexia in terms of purely right-hemisphere word processing." Their claim conflicts with the conclusions of previous published work, which strongly supports the RH hypothesis, work which they do not mention. Furthermore, I argue that their own results also favor the RH hypothesis (even though they claim otherwise); indeed, their results permit the formulation of a much more detailed version of the RH hypothesis than has hitherto been possible. Hence I conclude that the right-hemisphere interpretation of deep dyslexic reading remains the preferred explanation of deep dyslexia.