A technical guide to tDCS, and related non-invasive brain stimulation tools | Clinical Neurophysiology

Many of the leading tDCS researchers contribute to this Open Access article on clinical application of transcranial electrical stimulation (tES) techniques. Read it online, or download the pdf. (HatTip to Reddit user gi67)

  1. 1. Introduction
  2. 2. Transcranial direct current stimulation
    1. 2.1. Selecting and preparing electrodes and contact medium
    2. 2.2. Selecting and preparing electrode placement
    3. 2.3. Selecting a stimulation protocol
    4. 2.4. Use of blinding and sham
    5. 2.5. Safety versus tolerability
    6. 2.6. Considerations for transcutaneous spinal DC stimulation (tsDCS)
    7. 2.7. Considerations for cerebellar tDCS
      1. 2.7.1. Targeting the whole cerebellum
      2. 2.7.2. Targeting the cerebellar hemispheres
    8. 2.8. Selecting a stimulator
  3. 3. Transcranial alternating current stimulation (tACS)
    1. 3.1. Selecting tACS electrode placement
    2. 3.2. Selecting experimental design
    3. 3.3. Selecting stimulation parameters
    4. 3.4. Transcranial random noise stimulation (tRNS)
  4. 4. Monitoring physiological effects of tES
    1. 4.1. Monitoring physiological effects of tES with TMS
      1. 4.1.1. Monitoring of tES-induced motor cortex plasticity
    2. 4.2. Monitoring physiological effects of tES with electroencephalography (EEG) and event-related potentials (ERPs)
      1. 4.2.1. Selecting an approach
      2. 4.2.2. Integrating tES and EEG electrodes
      3. 4.2.3. Recording EEG during tES
    3. 4.3. Monitoring physiological effects of tES with magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS)
      1. 4.3.1. Integration of tDCS with MR
      2. 4.3.2. Considerations for concurrent MR acquisition
      3. 4.3.3. Other considerations for tDCS integrated with MR
  5. 5. Monitoring functional effects of tES
    1. 5.1. Monitoring functional effects of tES in healthy subjects
    2. 5.2. Monitoring functional effects of tES in patients
  6. 6. tDCS/tACS/tRNS in animal preparations
    1. 6.1. DC-, AC-, RN-induced membrane polarization
    2. 6.2. What can we learn from in vitro experiments?
  7. 7. tDCS and models of electric current through the brain
  8. 8. tES ethics
    1. 8.1. Education and training
    2. 8.2. Settings and procedures
    3. 8.3. Patient/subject selection
    4. 8.4. Patient/subject education and informed consent
  9. 9. Concluding remarks
  10. References

Scientists retrieve lost memories using optogenetics

I’m exposing my bias here, which is the hope that tDCS will be found to facilitate memory retrieval. This study, in mice, retrieved dormant memories using light (optogenetics) to activate cells used in memory formation. Recent studies suggest that memories are formed within a synaptic network, parts of which extend to areas of the brain more frequently targeted by tDCS. Probably closest to the research I’d like to see done (that I’m aware of) was reported in 2009, “Where Are Old Memories Stored in the Brain?“. I imagine a study where early memory, triggered by photos and recollections, are imaged using fMRI and that later, those same areas are targeted using tDCS. In the study reported on above, Medial Temporal Lobe Activity during Retrieval of Semantic Memory Is Related to the Age of the Memory, researchers concluded that older memories associated with regions in the frontal lobe, temporal lobe, and parietal lobe. (Though seems inconclusive as to whether memories are ‘stored’ there… “An additional way to understand the increasing involvement of some cortical areas, especially frontal cortex, as time passes is that older memories require more strategic, effortful search.”) Now, back to the post title article…

The researchers then attempted to discover what happens to memories without this consolidation process. By administering a compound called anisomycin, which blocks protein synthesis within neurons, immediately after mice had formed a new memory, the researchers were able to prevent the synapses from strengthening.

When they returned one day later and attempted to reactivate the memory using an emotional trigger, they could find no trace of it. “So even though the engram cells are there, without protein synthesis those cell synapses are not strengthened, and the memory is lost,” Tonegawa says.

But startlingly, when the researchers then reactivated the protein synthesis-blocked engram cells using optogenetic tools, they found that the mice exhibited all the signs of recalling the memory in full.

“If you test memory recall with natural recall triggers in an anisomycin-treated animal, it will be amnesiac, you cannot induce memory recall,” Tonegawa says. “But if you go directly to the putative engram-bearing cells and activate them with light, you can restore the memory, despite the fact that there has been no LTP.”

Source: Scientists retrieve lost memories using optogenetics
See Also: Neuroanatomy of memory
Gone But Not Forgotten? The Mystery Behind Infant Memories
The Hippocampus and episodic memory
Neuron Basics (video)

Cerebellum and processing of negative facial emotions…

Cerebellum and processing of negative facial emotions: Cerebellar transcranial DC stimulation specifically enhances the emotional recognition of facial anger and sadness.

Some evidence suggests that the cerebellum participates in the complex network processing emotional facial expression. To evaluate the role of the cerebellum in recognising facial expressions we delivered transcranial direct current stimulation (tDCS) over the cerebellum and prefrontal cortex. A facial emotion recognition task was administered to 21 healthy subjects before and after cerebellar tDCS; we also tested subjects with a visual attention task and a visual analogue scale (VAS) for mood. Anodal and cathodal cerebellar tDCS both significantly enhanced sensory processing in response to negative facial expressions (anodal tDCS, p=.0021; cathodal tDCS, p=.018), but left positive emotion and neutral facial expressions unchanged (p>.05). tDCS over the right prefrontal cortex left facial expressions of both negative and positive emotion unchanged. These findings suggest that the cerebellum is specifically involved in processing facial expressions of negative emotion.

via Cerebellum and processing of negative facial emoti… [Cogn Emot. 2012] – PubMed – NCBI.