This is a well-written review of the use of active touch by visually impaired and blind individuals to perceive objects and spatial patterns.
1) As it stands, the article is more limited in scope than its title, "Visually-impaired touch," would suggest. In particular, the article makes scant mention of the rather large body of literature on passive tactile perception among blind individuals, nor does the article consider non-spatial forms of tactile perception (e.g., vibrotactile perception, force perception, etc). As the article currently stands, an appropriate title would be "Visually impaired active spatial touch." I suggest the author expand the scope of his review somewhat by including a section on passive tactile spatial perception. The title of his review should perhaps be changed as well, to "Visually impaired spatial touch," in order to more clearly indicate its scope.
Passive tactile perception refers to the perception of stimuli pressed against the stationary skin (e.g, the fingertip). The field of passive tactile perception can best be divided, perhaps, into three subfields: studies of passive tactile spatial perception (e.g., perception of spatially patterned stimuli such as calipers, gaps and gratings) studies of passive vibrotactile perception (e.g., vibrotactile frequency discrimination), and studies of passive force perception (e.g., von Frey hair perception). A body of literature extending back several decades has investigated these areas, the first one (spatial perception) more extensively than the others.
The author would do well to create another section in his review to describe the findings from the literature on passive tactile perception. Since the authors' focus is primarily on object and spatial pattern perception, the author could focus the new passive tactile perception section of his review primarily on passive tactile spatial perception. Following are several prominent studies on passive tactile spatial acuity in blind individuals, that are not currently referenced:
Goldreich D, Kanics IM (2003) Tactile acuity is enhanced in blindness. J Neurosci 23:3439-3445.
Goldreich D, Kanics IM (2006) Performance of blind and sighted humans on a tactile grating detection task. Percept Psychophys 68:1363-1371.
Grant AC, Thaigarajah MC, Sathian K (2000) Tactile perception in blind braille readers: a psychophysical study of acuity and hyperacuity using gratings and dot patterns. Percept Psychophys 62:301-312.
Van Boven RW, Hamilton RH, Kauffman T, Keenan JP, Pascual-Leone A (2000) Tactile spatial resolution in blind braille readers. Neurology 54:2230-2236.
1) In discussing Braille reading speed and styles, the author would do well to reference a paper such as Davidson et al (1992): Davidson PW, Apelle S, Haber RN (1992) Haptic scanning of braille cells by low- and high-proficiency blind readers. Res Dev Disabil 13:99-111.
2) Aging and Developmental Issues section: Note that Goldreich & Kanics (2003, 2006), like Stevens et al. (1996) show decline in tactile acuity with aging. The author should reference those papers along with Stevens.
3) The author does not explain that Stevens et al (1996) - like Goldreich and Kanics (2003, 2006) - found clear evidence that, on passive spatial tasks, the acuity of blind individuals declined with age (acuity was better in the blind at any age, as mentioned by the author, but he does not mention that acuity of blind participants declined with age, in parallel with that of sighted participants). This stands in very interesting contrast to Legge et al., who found - with active touch - that blind individuals' acuity did not decline with age (as mentioned by the author). A brief mention of this interesting difference - and possible explanation for it - would be valuable for the readers.
4) The author mentions decline in cognitive function with age, but decline in tactile perception is also thought to occur because of loss of tactile receptors with age. See, for instance:
Bolton CF, Winkelmann RK, Dyck PJ (1966) A quantitative study of Meissner's corpuscles in man. Neurology. 16:1-9.
Bruce MF (1980) The relation of tactile thresholds to histology in the fingers of elderly people. J Neurol Neurosurg Psychiatry 43:730-734.
Cauna, N. (1965) The effects of aging on the receptor organs of the human dermis. In Advances in Biology of Skin (Montagna, W. ed), pp. 63-96, Pergamon Press.
5) The author discusses crossmodal plasticity, but does not also mention somatosensory cortical plasticity (another neural mechanism that might mediate sensory compensation). The review would be improved by mention of tactile experience-dependent somatosensory cortical plasticity, such as:
Pascual-Leone A, Torres F (1993) Plasticity of the sensorimotor cortex representation of the reading finger in braille readers. Brain 116:39-52.
Sterr A, Müller MM, Elbert T, Rockstroh B, Pantev C, Taub E (1998) Perceptual correlates of changes in cortical representation of fingers in blind multifinger braille readers. J Neurosci 18:4417-4423.
Sterr A, Muller M, Elbert T, Rockstroh B, Taub E (1999) Development of cortical reorganization in the somatosensory cortex of adult braille students. Electroencephalogr Clin Neurophysiol Suppl 49:292–298.
Reviewer B: I have the advantage of Reviewer A's excellent comments.
I must strongly reinforce the suggestion that the article be renamed. It is far too narrow for the current content, which primarily relates to 2D pattern perception. Even adding "spatial" does not fit, because, for example, this could include 3D object processing or navigation. Also, the syntax is awkward: it is not the touch that is visually impaired. I would therefore suggest, Visual impairment and pattern perception
To the list of omitted papers I would add Loomis's analysis of the filtering properties of skin and its relation to Braille, i.e., Braille appears to be an optimal pattern set under the constraints of skin filtering and fingertip size.
The article is still called "visually-impaired touch" which I find inappropriate. As I said previously, "Visual impairment and pattern perception" (suggested by another reviewer) would be far more appropriate, as this deals primarily with 2D pattern perception. If the author is unwilling to change, something should be entered here.
I also find the list of readings to be quite narrow. Only books by Heller are mentioned. How about Cataneo and Vecchi, "Blind Vision." But there are others: Hatwell, Millar, Rieser.
Even more comments
The current version of the article is much improved. I do have several suggestions, however:
1) The author references Sathian (2000) in support of the sensory compensation hypothesis. In addition to that review article, the following original research articles providing support for the sensory compensation hypothesis should be referenced:
Van Boven RW, Hamilton RH, Kauffman T, Keenan JP, Pascual-Leone A (2000) Tactile spatial resolution in blind braille readers. Neurology 54:2230 –2236.
Wong M, Gnanakumaran V, Goldreich D (2011) Tactile spatial acuity enhancement in blindness: Evidence for experience-dependent mechanisms. The Journal of Neuroscience 31: 7028–7037.
2) In the "Aging and Developmental Issues" section, the author writes that:
"However, recruitment of the visual cortex in blind individuals might explain their better tactile and haptic perception (Cohen et al., 1997) as has been found more recently in short-term blindfolded sighted participants (Weiser et al., 2005)."
This sentence is worded ambiguously. It is unclear from the wording whether Weiser et al. reported that short-term blindfolded sighted participants have show tactile recruitment of visual cortex, or whether they show better tactile and haptic perception, or both. The sentence should be rephrased to clarify. Also, the author should clarify what is meant by "recruitment" and by "visual cortex" here, as Weiser reported effects (not always activation; in some cases deactivation), not in primary visual cortex but rather in probable areas V3A and vIPS.
The author should also discuss the results of the following paper, with respect to the (limited) effects in visual cortex of short-term visual deprivation of sighted participants:
Merabet LB, Swisher JD, McMains SA, Halko MA, Amedi A, et al. (2007) Combined activation and deactivation of visual cortex during tactile sensory processing. J Neurophysiol 97: 1633–1641.
Finally, relevant to the perceptual effects of short-term visual deprivation of sighted participants, the author should reference a recent study showing that short-term light deprivation does not improve passive tactile spatial acuity:
Wong M, Hackeman E, Hurd C, Goldreich D (2011) Short-term visual deprivation does not enhance passive tactile spatial acuity. PLoS ONE 6(9): e25277.
3) Minor writing suggestions:
-- In the "Braille" section, the author writes that "Braille characters are just over 6 mm tall." I suggest rather than using the word "tall," the author provide the "length" and width of a Braille cell. The reason for using "length" instead of "tall" is that "tall" may be mistaken by the reader to indicate the height above the page of the embossed dots (i.e. the relief or z-axis of the cell).
- In the "Aging and Developmental Issues" section, the author writes that "It is well known that aging affects cognitive processing and the brain activity and function. (Park et al 2001)." This should be "...cognitive processing and brain activity..." (remove "the").
-- In the "Passive Tactile Perception in Blindness" section, the author writes that "Gibson argued that passive touch is atypical and prompts subjective sensations, however, many useful sensory aids for blind people make good use of passive touch." The comma before "however" should be changed to a semicolon.
More comments from B Sept 24, 2012
It is still rather author-centric, but this may be appropriate given the topic. My previous comments about title remain in force. The following comments point to sections and alternate text and reviewer response.
Section: Pictures and Pattern Perception by [[reviewer's edit] blind people
found better performance with raised-line pictures if they are larger Reviewer: "better' than what?
Of course they do not. Reviewer: But they do, on the retina. That is the result of perspective viewing.
since perspective involves direction Reviewer: unclear what is meant by "involves direction"
Moreover, if straight ahead on the map Reviewer: Meaning of straight ahead depends on how the map is held. Does the writer mean upward on the map, if held parallel to the frontal plane?
just as in the sighted. Reviewer: use "for" the sighted, as in previous clause
Reviewer: Aging and Developmental Issues: Reviewer: Why so much detail in the first paragraph about the Ballesteros study, in comparison to the sparse description of other studies? The point seems to be missing in the details.
"Dimensional structure was…" Reviewer: This is not good syntax.
The findings discussed above agree with the sensory compensation hypothesis Reviewer: Start a new paragraph here
two hours of blindfolding Reviewer: this sounds like two hours to put on a blindfold. Repalce with two hours of blindfolded experience
Conclusions: Many studies demonstrate advantages in pattern perception in the late blind Reviewer: Relative to what?