Measuring Brains Before Conventional Computers?

Would you believe me if I said we’ve been measuring brain activity long before traditional computers even existed? In the 1954 paper titled, “A summation technique for the detection of small evoked potentials”, Dawson proposes an updated mechanism to capture a person’s neural activity when they respond to a stimulus. For context, he was living in interesting times where other scientists like Brazier and Casby would use Lee’s method to electronically detect small evoked responses. But how was Dawson different? He wanted to create a mechanical machine to sample this brain activity. I think it’s worthwhile to study this system because it can be intuitive despite being unconventional to our very digital age way of thinking. Let’s check out Dawson’s system!

The Distributor and Storage Unit: A and B are two distributors. Cs1—62 are one bank of storage capacitors. G1, G2, and G3 are the reduction gears. K1 and K2 are the timing contacts that initiate the stimuli, charge the store, and start the display sweeps. M is the 50 c/sec synchronous driving motor.

The Distributor Unit: C is the insulating spindle that revolves ball bearings in the end plates at P. Then it carries the rotating contacts of two distributors at A and B. There is an earthed screen at E that separates the units and screens D and F. The screens are maintained at the same potential as the rotors in the distributors at A and B to reduce capacity from the rotors to E.

A scheme of the apparatus used for averaging: Sla and Slb are the two distributors. Ca1 to Cs62 the storage capacitors on one of them, and K1 and K2 are contacts closing 10 times a second and once a second respectively. G1, G2 and G3 are gear boxes giving the reductions shown. The input signal is observed on CRT 2 and the average waveform on CRT 1.

Does it seem confusing? I’ll be honest, I’ve read this paper a couple of times and I still don’t fully understand how this mechanical system can average large spontaneous EEG activity in the brain with simple oscillograms. Despite that, it’s kind of… beautiful. I love how this paper uses a detailed appendix to show the schemas, circuit diagrams, and photographs of the Dawson machine. It helps remind you of times where even brains can benefit from mechanical solutions, despite electronic systems being prevalent. Broadly, I’d like to see a paradigm shift in neurotechnology — to favour hardware and mechanical firmware solutions when possible (even if it’s more difficult than digital systems).

The Blind Mind: Can Aphantasiacs Not Access Their Imagination?

Aphantasia is the inability to visualize. Otherwise known as image-free thinking.

People with aphantasia don’t create any pictures of familiar objects, people, or places in their mind’s eye.

Do you have aphantasia?

The Imagination Test: Close your eyes and imagine an apple. What do you see?

Social context

People realizing their mind is blind

A research article aimed to clarify the nature of congenital aphasia, whether a person without neurological damage could either not visually imagine an object or not access the images they imagined in their head due to limited introspection and metacognition (Keogh and Pearson, 2018). Past research explored this debate in visual imagery by labelling it either as depictive or propositional throughout the 1970s and 80s. However, recent research metricized this imagery paradigm phenomenon by introducing questionnaires, neuroimaging techniques centered on the visual cortex, and mental rotation tasks. These techniques relied on measuring sensory priming effects, instead of depending on self-reports, by showing a background image when the person was actively imagining objects, which would conflict with their cognitive resources. This study predicted that if a person with congenital aphasia lacked visual imagery, they wouldn’t show priming effects. If congenital aphasia was triggered by limited metacognition, the researchers hypothesized the person would not report mental imagery but would still show a priming effect.

To explore these predictions, the study recruited fifteen consensual people with self-reported aphantasia in the 21-68 age range from an online social media page. They had normal or corrected-to-normal vision, were not screened with a neurological exam, and incentivized with an hourly pay for the 3-hour study and a de-briefing. The control group was based on data from previous experiment results with 209 participants, run under the same stimuli paradigm and experimenter for consistency. Researchers used a binocular rivalry visual imagery task with questionnaires and an assessment to explore a person’s visual imagery ability without the influence of eye dominance as a confound. Each person was placed in a dark room with a monitor that showed two different images, a green-vertical or red-horizontal Gabor patch, to each eye. In the 60-trial experimental timeline, they were cued with an “R” or “G” visual to imagine either patch and shown an imagery period with either a luminance or no luminance condition for 6 seconds. The former showed a consistent black background display during the experiment whereas the latter showed a yellow background, to limit visual attention transients, that increased and decreased during the beginning and end of the 6-second task for 40 trials per block. The participant then rated the vividness of the image they imagined on a 1-4 scale, was shown a binocular rivalry display, and prompted to answer if they saw a green-vertical, perfectly mixed, or red-horizontal Gabor patch labelled as 1-3 respectively. Each person also answered three questionnaires that included, the vividness of visual imagery questionnaire (VVIQ2) on a 1-5 scale, spontaneous use of imagery scale (SUIS), and object and spatial imagery questionnaire (OSIQ) with statements rated from 1 to 5 on agreeableness.

To evaluate the researchers’ hypotheses, the following results explored which imagery paradigm phenomenon was consistent with congenital aphantasia’s symptoms. On the questionnaires, the participants with aphantasia rated poor visual imagery and spontaneous use on the VVIQ, SUIS, and OSIQ’s object factor respectively. However, they showed a significant effect with double the spatial effect, compared to an object component, with an ANOVA under mixed repeated measures. For the binocular rivalry imagery task, aphantasics showed no significant visual priming effect when compared to the control group. During the imagery period, the participants with aphantasia also showed a non-significant priming effect and vividness rating in neither luminance nor no luminance conditions. Thus, they confirmed an aphantasic person’s imagery did not affect binocular rivalry and supported the researchers’ hypothesis of a limited low-level visual imagery ability. Lastly, the findings included a bootstrapping resampling analysis with a 15-person pilot study to account for a representative control group mean visual priming score, recorded 1000 times, in contrast to the small aphantasic sample size. The iterations confirmed the results were not based on a random probability since the control group had a P = 0.001 chance to have the same mean priming score as the aphantasics.

Overall, these findings confirmed the study’s hypothesis that a person with congenital aphantasia showed no priming effects because they simply could not visually imagine a low-level object, not due to a lack of metacognition. Based on previous research, these results support the link of a ventral stream deficit to aphantasics who cannot use their early visual cortex to imagine items but can have spatial imagery and mentally rotate objects. However, the inconsistencies in the study’s methods with variances in stimuli vividness ratings, inconsistent monitor sizes, and non-completed trials due to time constraints could have jeopardized the generalizability of the control group’s data and should be replicated. Though, this study ensured measure validity with low-level visual imagery by using a binocular rivalry illusion that eliminated alternate explanations like an eye dominance bias, kinaesthetic imagery, propositional semantic information, etc. While the participants did not undergo a formal neurological assessment to confirm their aphantasic status, the researchers ran mock-rivalry trials and mental rotation tasks to exclude demand characteristics like a person choosing to suppress their imagination instead of truly not having the capacity to do so. For future directions, the study would benefit from consistent experiment methods that test other cognitive variances with high resolution neuroimaging, like fMRI, in the dorsal and ventral visual processing streams of aphantasics.

References

Keogh, R., & Pearson, J. (2018). The blind mind: No sensory visual imagery in aphantasia. Cortex, 105, 53–60. https://doi.org/10.1016/j.cortex.2017.10.012

How "Old" is the Concept of the Brain?

Did you ever wonder when the brain was formally defined? Well, the earliest reference of the word “brain” in human records is found in an ancient Egyptian document called the Edwin Smith Surgical Papyrus, dating back to 17th century BC!

Edwin Smith Surgical Papyrus

It's also the 1st medical document in the history of mankind. This medical document primarily highlighted the symptoms, diagnosis, and treatment of 28 head/spine injury cases! Like:

  1. Associating a temporal lobe fracture with aphasia

  2. Spinal cord injury with quadriplegia

  3. Lasegue’s sign for nerve irritation

Very impressive for it's time! In fact, the ancient Egyptians further described the brain's wrinkles (composed of gyri/sulci) and heart pulse as:

"those ripples that happen in copper through smelting, with a thing in it that throbs and flutters under your fingers like the weak spot of the crown of a boy before it becomes whole."

Throughout the surgical papyrus, you'll see some ancient neuroanatomy terms (that are commonly used today!) Written in hieroglyphs, from left to right: the word "brain", cerebrospinal fluid, the meninges (protective membrane layer), and cerebral cortex convolutions (wrinkles):

Sadly, the brain itself was considered a useless organ to the ancient Egyptians! So when mummifying, they would scoop it out via the nostrils and throw it away, unlike the heart, which was left in every body because they believed it housed a person’s intellect & emotional being. Oh, how things have changed. But still, having a big brain is no excuse to have a small heart, so be careful what you choose to optimize for.

Scooping the brain out of the mummy