Open-source rTMS device design, part 4
by quicksilv3rflash

2019-03-17: Good news. The prototype is working. Now, it's certainly in no condition to ship... but it's finally working! I personally am greatly relieved — the feeling of having already accepted preorder money to buy parts to build something that isn't yet functional is pretty distressing to me. I don't know how all those people on kickstarter could do it; I guess I just don't have the right personality type for selling false promises. The trouble with engineering, of course, is that until the prototype is tested and working (today!) you can never be really certain that your plans will work. So what now? Well, I still need to do more tests. All I've done is fire the thing up and verify that it sounds right (the pulses are audible, it's a low-frequency buzz currently set at 33Hz for testing), and check that the capacitor voltages are correct. I need to use an inductive current probe to get pictures of the output current waveform, and put the whole circuit into a simulator, and get the simulator to match what I'm measuring. Then I need to specify parts for the full power version — currently I've got a 1300V 130uF capacitor for the main pulse capacitor, that needs to become a 3000V 220uF capacitor to match the power output capacity of the Magstim Rapid, and all the other parts need to be increased in voltage rating proportionally. I'll have a parts list pretty soon and I'll be contacting everyone who has preordered to work out logistics to get the devices out to them.

https://www.reddit.com/r/rtms/comments/9nvdh1/opensource_rtms_device_design_part_4/

No longer science fiction: Brain-to-brain interfaces can transmit thoughts | Genetic Literacy Project

https://geneticliteracyproject.org/2019/03/25/no-longer-science-fiction-brain-to-brain-interfaces-can-transmit-thoughts

There is a cognitive bias that leads to the fact that there is not enough meaning, this is also due to the fact that we simplify probabilities and numbers to make them easier to think about, and this happens also because there is a magic number 7+-2, which correlates with the size of the working memory in the brain. It is difficult to say whether there is much meaning in increasing the working memory, but one can definitely say that without increasing the working memory, there is less meaning.

32-channel EEG brain-computer interface FreeEEG32 is designed and produced for measuring working memory, and an alternating current stimulator FreetACS is produced to increase working memory.

https://upload.wikimedia.org/wikipedia/commons/a/a4/The_Cognitive_Bias_Codex_-_180%2B_biases%2C_designed_by_John_Manoogian_III_%28jm3%29.png

US Military funds mind-reading helmet that may let soldiers TELEPATHICALLY control robots or drones and could even give the gift of sight to the blind

The Defense Advanced Research Projects Agency gave $18 million to the project
Researchers will use gene therapy to help human brains interact with a helmet
If realised the tech could allow thoughts to be transferred from brain to machine
The helmet may also allow for one person's vision to be shared with another

https://www.dailymail.co.uk/sciencetech/article-7111199/US-Military-funds-mind-reading-helmet-let-soldiers-TELEPATHICALLY-control-robots-drones.html

Functional harmonics reveal multi-dimensional basis functions underlying cortical organization

The human brain consists of functionally specialized areas, which flexibly interact and integrate forming a multitude of complex functional networks. The principles underlying this functional differentiation and integration remain unknown. Here, we demonstrate that a fundamental principle ubiquitous in nature - harmonic modes - explains the orchestration of brain's functional organization. Applied to the functional connectivity in resting state averaged across 812 participants, harmonic modes give rise to functional harmonics revealing the communication channels of the human brain. Each associated with a different spatial frequency, the functional harmonics provide the frequency-ordered building blocks, which can reconstruct any pattern of brain activity.

https://www.biorxiv.org/content/10.1101/699678v1

Neuralink update https://www.teslarati.com/neuralink-project-demo-event-livestream-july-16/

An integrated brain-machine interface platform with thousands of channels

Elon Musk, Neuralink

doi: https://doi.org/10.1101/703801

Brain-machine interfaces (BMIs) hold promise for the restoration of sensory and motor function and the treatment of neurological disorders, but clinical BMIs have not yet been widely adopted, in part because modest channel counts have limited their potential. In this white paper, we describe Neuralink's first steps toward a scalable high-bandwidth BMI system. We have built arrays of small and flexible electrode "threads", with as many as 3,072 electrodes per array distributed across 96 threads. We have also built a neurosurgical robot capable of inserting six threads (192 electrodes) per minute. Each thread can be individually inserted into the brain with micron precision for avoidance of surface vasculature and targeting specific brain regions. The electrode array is packaged into a small implantable device that contains custom chips for low-power on-board amplification and digitization: the package for 3,072 channels occupies less than (23 x 18.5 x 2) mm3. A single USB-C cable provides full-bandwidth data streaming from the device, recording from all channels simultaneously. This system has achieved a spiking yield of up to 85.5% in chronically implanted electrodes. Neuralink's approach to BMI has unprecedented packaging density and scalability in a clinically relevant package.

https://www.biorxiv.org/content/10.1101/703801v1

Analyzing combined eye-tracking/EEG experiments with (non)linear deconvolution models

Fixation-related potentials (FRPs), neural responses aligned to saccade offsets, are a promising tool to study the dynamics of attention and cognition under natural viewing conditions. In the past, four methodological problems have complicated the analysis of combined eye-tracking and EEG experiments: (i) the synchronization of data streams, (ii) the removal of ocular artifacts, (iii) the condition-specific temporal overlap between the brain responses evoked by consecutive fixations, (iv) and the fact that numerous low-level stimulus and saccade properties also influence the post-saccadic neural responses. While effective solutions exist for the first two problems, the latter ones are only beginning to be addressed. In the current paper, we present and review a unified framework to deconvolve overlapping potentials and control for linear and nonlinear confounds on the FRPs. An open software implementation is provided for all suggested procedures. We then demonstrate the advantages of this analysis approach for three commonly studied free viewing paradigms: face perception, scene viewing, and natural sentence reading. First, for a traditional ERP face recognition experiment, we show how deconvolution can separate stimulus-ERPs from the overlapping muscle and brain potentials produced by small (micro)saccades on the face. Second, in natural scene viewing, we isolate multiple non-linear influences of saccade parameters on the FRP. Finally, for a reading experiment using the classic boundary paradigm, we show how it is possible to study the neural correlates of parafoveal preview after removing the spurious overlap effects caused by the difference in average fixation time. Our results suggest a principal way of measuring reliable fixation-related potentials during natural vision.

https://www.biorxiv.org/content/10.1101/735530v1

Agency and responsibility over virtual movements controlled through different paradigms of brain-computer interface

Agency is the attribution of an action to the self and is a prerequisite for experiencing responsibility over its consequences. Here we investigated agency and responsibility by studying the control of movements of an embodied avatar, via brain computer interface (BCI) technology, in immersive virtual reality. After induction of virtual body ownership by visuomotor correlations, healthy participants performed a motor task with their virtual body. We compared the passive observation of the subject's 'own' virtual arm performing the task with (1) the control of the movement through activation of sensorimotor areas (motor imagery) and (2) the control of the movement through activation of visual areas (steady-state visually evoked potentials). The latter two conditions were carried out using a brain-computer interface (BCI) and both shared the intention and the resulting action. We found that BCI-control of movements engenders the sense of agency, which is strongest for sensorimotor areas activation. Furthermore, increased activity of sensorimotor areas, as measured using EEG, correlates with levels of agency and responsibility. We discuss the implications of these results for the neural bases of agency, but also in the context of novel therapies involving BCI and the ethics of neurotechnology.

https://www.biorxiv.org/content/10.1101/735548v1

The CMU Array. A 3D Nano-Printed, Fully Customizable Ultra-High-Density Microelectrode Array

Microelectrode arrays (MEAs) provide the means to record electrophysiological activity fundamental to both basic and clinical neuroscience (e.g. brain computer interfaces). Despite recent advances, current MEAs have significant limitations, including recording density, fragility, expense, and the inability to optimize the probe to individualized study or patient needs. Here we address the technological limitations through the utilization of the newest developments in 3D nanoparticle printing. Our CMU Arrays possess previously impossible electrode densities (> 6000 channels/cm2) with tip diameters as small as 10um. Most importantly, the probes are entirely customizable owing to the adaptive manufacturing process. Any combination of individual shank lengths, impedances, and layouts are possible. This is achieved in part via our new multi-layer, multi material, custom 3D-printed circuit boards, a fabrication advancement in itself. This device design enables new experimental avenues of targeted, large-scale recording of electrical signals from a variety of biological tissues.

https://www.biorxiv.org/content/10.1101/742346v1

Low-frequency Neural Activity Reflects Rule-based Chunking during Speech Listening

Cortical activity tracks the rhythms of phrases and sentences during speech comprehension, which has been taken as strong evidence that the brain groups words into multi-word chunks. It has prominently been argued, in contrast, that the tracking phenomenon could be explained as the neural tracking of word properties. Here we distinguish these two hypotheses based on novel tasks in which we dissociate word properties from the chunk structure of a sequence. Two tasks separately require listeners to group semantically similar or semantically dissimilar words into chunks. We demonstrate that neural activity actively tracks task-related chunks rather than passively reflecting word properties. Furthermore, without an explicit 'chunk processing task,' neural activity barely tracks chunks defined by semantic similarity - but continues to robustly track syntactically well-formed meaningful sentences. These results suggest that cortical activity tracks multi-word chunks constructed by either long-term syntactic rules or temporary task-related rules. The properties of individual words are likely to contribute only in a minor way, contrary to recent claims.

https://www.biorxiv.org/content/10.1101/742585v1