visual imagery deficiency

Posted comment on ´Blind in the Mind` by D Grinnell and published in New Scientist 23rd April 2016 3070 p34

SUMMARY

The author of the article, D. Grinnell, has never been able to carry out mental imagery, but claims he has no problems with tasks that are usually aided by it, eg. navigation and people recognition. He appears not to be unique with 2-3% of people also lacking the capability according to a study using the test, Vividness of Visual Imagery Questionnaire, where various scenes have to be imagined and the clarity of the mental picture rated. The idea that some people are not capable of forming mental images is not new with Sir Francis Galton reporting it as early as 1880. He asked his study participants to imagine things on a breakfast table and found that some were unable to carry out the required task.

Grinnell in his article quotes a study by Zeman and colleagues whose subject, MX, was a 65 year old building surveyor who reported losing the capability to form mental images after heart surgery. MRI scans showed that when pictures of recognizable things were shown to MX, firing patterns were produced in visual areas towards the back of brain and these patterns were both expected and distinctive. Attempts by MX to imagine the same pictures however, produced no such firing patterns. Although the mental images could not be formed, it was found that MX could still give relevant information about the objects such as the number of windows in a particular house. The condition of lack of mental imagery was named as aphantasia by Zeman and his colleagues who also found in their study a further 21 people suffering from it, all of whom appeared to have had it from birth. Zeman concluded that a person does not have to see something to ´live it`, they just needed to be aware of it and Grinnell, himself a sufferer, in his article agrees with this view.

In his article, Grinnell went on to describe the psychological hypotheses relating to visual imagery. The cognitive neuroscientist, Kosslyn, described visual imagery as depictive/ quasipictorial representations and that spatial organization of brain activity resembles the object imagined. Kosslyn explained visual imagery from a physiological perspective by saying that visual imagery is not constructed in a single way in the brain because the separate visual circuits for shape, colour and spatial relationships are not all switched off in aphantasia. Grinnell found on questioning aphantasics that visual imagery was replaced by imaginary drawing and therefore, there was control of physical movements such as finger movements. This hypothesis was supported by Zeman and team. In their tests on MX, Zeman´s group also found that MX`s spatial rotation skills were faster than average. Spatial rotation requires the subject to say which images are the same as the guide image, only rotated and hence, the greater the rotation, the longer the time required to work out if there is a match because of the need for mental image manipulation. To explain their observations, Zeman believes that everyone has visual capabilities and people with mental imagery rely on this visual information whereas aphantasics are given other information or representations. This is supported by evidence that aphantasics dream in pictures and some see flashes of imagery under certain conditions, eg. before they fall asleep. Therefore, aphantasics may not be able to consciously control their mental pictures, but the capability to carry them out may not itself have vanished.

Grinnell continues in his article by citing Zeman`s hypothesis of the parallels between aphantasia and blindsight. In blindsight, there is visual information, but no conscious awareness of it. De Vito and Bartolomeo extended this by saying that aphantasics still have the capability to imagine, but just believe they cannot thus supporting Zeman`s hypothesis. It was proposed that extreme stress could induce a change to aphantasia and evidence from a study of Monsieur X in 1883, who after a period of intense anxiety developed aphantasia, was given. However, this could not be said to apply to other well-known cases including MX whose aphantasia was caused by brain injury and by Grinnell himself who was born with the condition.

Grinnell in his article also discussed whether aphantasia was reversible. Pearson in Australia looked at whether mental imagery could be reset. In 2008, a test was developed that objectively measured peoples` mental imagery capability. Subjects` fields of vision were divided so that they saw a set of horizontal red stripes through one eye and a set of vertical green stripes through the other. Normally, one set is perceived first, but if flash cards are displayed quickly several times then for most people the probability of perceiving that particular colour the first time increased. This was explained by the formation of the picture in the subject`s mind`s eye which led to priming of the participant to see it again. However, studies on aphantasics gave inconsistent results. Pearson then coached those participants that demonstrated the unconscious mind`s eye by saying that they had to try visualizing either the green or red striped pattern for a few seconds every day for 5 days. The process was then repeated in the laboratory and the participants were asked to rate the strength of the image. Immediately afterwards, Pearson flashed the red pattern in one eye and the green in the other and measured whether people had perception bias. In some cases, the objective rating was found to remain constant, but the subjective rating had improved suggesting that the training had helped people to begin to access the previously subconscious mind`s eye. Grinnell himself found shapeless lights flashed into his mind, but decided not to continue with the training.

Grinnell`s article concluded with him saying that aphantasia had given him an unique way of seeing the world which he did not want to relinguish. Others also stressed the importance of aphantasia and the unique skills required for people lacking mental imagery to carry out cognitive processes. This capability could be used to determine alternative ways of information processing and thinking which could aid those suffering from neurological disorders.

COMMENT

What makes this article interesting is that aphantasia appears to go against what we think is happening with the neurochemical mechanisms in the cases of certain cognitive capabilities such as complex decision-making or navigation. In such examples we believe that imagined visual information built in the mind, albeit based on ´real` information whether in real-time or from memories, helps the brain to carry out the required tasks. However, it is clear that there are certain people, the aphantasics, who have no visual imagery, possess neurochemical mechanisms that are obviously different to others, but are still able to perform normal cognitive tasks such as decision-making. Therefore, there is a need to investigate the neurochemical mechanisms of this minority of people. For  97-98% of people capable of seeing, visual information plays an important role in memories, thinking and informational processing and to carry out these functions there are various visual systems and mechanisms employed including: the physiological visual neuronal pathway from input in the eye to the higher cortical areas; visual short term memory where visual information is held as an electrical firing pattern for a very short period of time (less than 10 seconds) and the person may be conscious of the experience or unconscious; visual long term memory where neuronal cell assemblies are formed from the short term visual firing patterns and the information is stored as memories to be consciously or unconsciously recalled at a later date; the visual buffer which is part of the Baddeley and Hitch working memory model and is the processing ´work space` of the cognitive brain; and finally, and obviously not for everyone, visual imagery which is defined as where there is a visual memory representation when the stimulus is not actually being viewed, ie. ´seeing with the mind`s eye`.

The various visual systems and mechanisms are well-researched and new knowledge is continually being added and from this collection of knowledge we know that visual representations are part of decision-making for example, thought (Aristotle`s view that they are the ´medium of thought`), problem-solving, prospective memory planning and memory techniques such as method of loci. The visual images are formed in the V1 with involvement of the V2, slightly elongated fields and have close similarities to perception even though they are lower in detail than those spawned from ´real` stimuli. In the majority of people the visual representations formed in the V1 are likely to follow Kosslyn`s perceptual anticipation theory with the images being quasipictorial representations.

However, aphantasics show that visual imagery is not necessary in their case for the same cognitive capabilities to be demonstrated as those having this capability and therefore, their neurochemical mechanisms are likely to be different to those of the majority. In fact, they are examples of support for the Pylyshyn`s propositional theory for visual imagery where the visual image is not dependent on depictive/quasi pictorial representations, but a tacit knowledge of how the subject would ´look` in the situation. This could possibly be explained by considering the information at V1 not as solely visual, but as instead electrical representations that are capable of being interpreted into a visual image if required or more likely a multi-sensory representation with input included from the other sensory systems as well. Such a representation would override the need for visual dominance in cognitive functioning and allow aphantasics to process information in the absence of conscious visual imagery, but using the unconscious information from visual pathways and other senses. Therefore, aphantasics have a lack of awareness that visual information is being used, only that an electrical representation is formed. This view is supported by observations that: the visual imagery capability is still present in aphantasics since studies have shown that people can be trained to some degree to use it; conscious visual information is not always required since in others there are plenty of examples of unconscious visual processing such as moving before knowing why you have to move; and the cases of blind sight and visual working memory where visual information is being processed without conscious awareness.

What makes this topic interesting is that aphantasics provide a relatively large subject group in experimental terms that are likely not to suffer from mental health issues, or brain injuries and who could allow the conditions and mechanisms of mental tasks to be explored to the full, eg. decision-making or prospective memory. Not only could objective research methods be employed, but introspection could be considered more repeatable and reliable. Studies using techniques such as imaging, temporary incapacitation of certain brain areas with tDCS for example or local anaesthetics could explore the mechanisms involved in the cognitive processing of aphantasics and perhaps shed light on new approaches to, for example, the treatment of mental disorders affected by deficient information processing. In his article, Grinnell refuses to continue with the training to overcome his lack of visual imagery preferring his uniqueness and he may be helping the rest of us by doing so!

Since we`re talking about the topic………………….

……since visual imagery is presumed to be required for matching objects that have been rotated to some degree, would accurate imaging studies show the mechanisms that aphantasics employ in the carrying out this skill?

……if training with flash cards changes the performance of aphantasics to ´seeing images`, could training using images of clocks aid prospective memory performance in those suffering from disorders where information binding is problematic?

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