Cool New Technologies for Studying the Brain Optical illusions; Invisible Gorilla; Experimenter/listener/patient bias;

Anatomy Selective stains (e.g. Golgi stain as used by Cajal) Dyes, antibodies Single-cell intracellular labelling CAT scans MRI fMRI DTI “Brainbow” “Clarity”

MRI (Magnetic Resonance Imaging) Based on NMR (nuclear magnetic resonance) Looks at Hydrogen atoms – sensitive their environment fMRI – “functional” MRI Sensitive to the amount of Oxygen bound to hemoglobin Assumed to reflect amount of neuronal activation DTI – Difusion tensor imaging Looks at how “free to move” are the Hydrogens on water (H2O) Appears to be useful for identifying “fiber tracts” (axons)

fMRI And in another experiment (see fMRI below), listening to one stimulus while watching another, unrelated, one, led to reduced brain activity when compared with listening alone or looking alone.

Diffusion Tensor Imaging

“Brainbow” Method B-B-B B-B-P B-B-R R-R-R R-R-G R-G-G G-G-G G-G-B G-B-B

“Brainbow - Results Brainbow is the process by which individual neurons in the brain can be distinguished from neighboring neurons using fluorescent proteins. By randomly expressing different ratios of red, green, and blue derivatives of green fluorescent protein in individual neurons, it is possible to flag each neuron with a distinctive color.

“Clarity”

Conditional Optogenetic “knock in” Figure 1. Activity-dependent labeling of neurons. (A) Training-induced neuronal activity drives the expression of tTA, which in turn activates downstream gene expression through TRE promoter and labels active cells with ChR2-EYFP (yellow). This process can be blocked by the presence of Dox. (B) The animals are kept on Dox (green background) before the training, so any irrelevant stimuli (represented by various symbols) during this period will not cause cells to express ChR2-EYFP. The animals are taken off Dox during training, so cells active during the memory formation will be labeled. Animals are put back on Dox diet post-training and during testing, so no further labeling happens.

Demonstration of False Memory in Rats using Optogenetics FIGURE 2 | Inception of a false fear memory. Top: The behavior paradigm for the experimental animals. Animals were kept on Dox post-surgery (green background), then taken off Dox and allowed to explore context A to label active cells with ChR2. Then they were put back on Dox and fear conditioned (lightning symbol) in context B while receiving light stimulation (blue shower symbol) to activate cells representing context A. When they were put back to context A, they showed a false fear memory for A (freezing indicated by wavy lines) where they were never actually shocked. They showed no fear memory for a control context C and a genuine fear memory for context B where they were shocked. Bottom: Cellular activity. Red, gray, and white circles indicate neurons representing contexts A, B, and C respectively. Asterisks indicate neurons activated either naturally by contextual exposure or artificially by light stimulation Now “A” = shock Red Cells=“A” Grey Cells=“shock” Red cell assoc. v/schok

Downstream activity elicited by “natural” and “false” memory (C) Three groups of mice underwent the training shown in (A) and were euthanized after testing in either context B (natural recall), A (false recall), or C (neutral context). The percentage of c-Fos–positive cells was calculated for each group in basolateral amygdala (BLA) and central amygdala (CeA) (n = 6 subjects each; ***P < 0.001). (D to F) Images for natural recall, false recall, or neutral context. Creating a False Memory in the Hippocampus, Science 341, 387 (2013); Ramirez et al.

Techniques for studying the brain - Summary All techniques have their uses and limitations Heisenbergian “the more one controls, the less one ‘lets the system do’” Remember “compared to what” – placebo/sham is best comparator To obtain useful data, one must have a well-designed experiment Proper “blinding” is very important Statistics must be used properly The interpretation of results from any technology is subject to revision Epigenetics “Chimerism” ??? CLever han

Some Parting Thoughts Most human brains have the same basic structure, but all also unique Brain function is dependent on (and limited by) the “modules” it contains Much brain function occurs beyond the reach of “consciousness” The brain is constantly changing (plasticity), but some plasticity is easier during “critical periods” Reality is a construct of the brain; the brain is fallible and differently fallible in everyone. “You can’t believe everything you think”; and, confidence is an unreliable predictor of accuracy. Brain disorders are common and usually not a matter of “will power” or “character” Good science (e.g., double-blind) is the best way to make progress in understanding the brain.

Thank you for your attention Questions? Comments?