Ken Dychtwald - The Consequences of Human Life Extension

A very interesting and well-delivered talk on aging and the inevitable and dramatic changes that will take place in society and in individual lives over the coming decades as people in the West grow increasingly older and older and older. Also available on iTunes.

http://www.longnow.org/seminars/02004/dec/03/the-consequences-of-human-life-extension/

One memorable quote: “Of all the humans who have ever lived over 65, two-thirds are now alive now.”

Brembs (2006) Brains as output/input devices

I just finished reading an excellent blog post (paper?) by Björn Brembs entitled Brains as output/input devices. I admit that I too have tended to think of brains as stimulus-response machines, paying little attention to spontaneous behaviour and operant learning. Indeed, the old iPlant programming section on my website used to begin "Like a digital computer, the brain generates output from input". On the contrary, Brembs argues, the brain generates input from output. That is, the main function of brains is to control the environment they're in - and thus the sensory input and rewards/punishments they receive - by figuring out the right motor output for a given situation.

"input/output transformations may only account for a small fraction of what brains are doing. Maybe a much more significant portion of the brain is occupied with the ongoing modelling of the world and how it might react to our actions?"

Furthermore, Brembs argues, the variability we observe in spontaneous behaviour is a feature of operant learning: it is a way for the brain to find and develop patterns of behaviour that give it optimal control over its environment. "Faced with novel situations, humans and most animals spontaneously increase their behavioural variability", presumably in order to figure out how this particular environment responds to behaviour. It's the environment that responds, not the animal. Perhaps even the subtle variability we see in the invertebrate feeding system is an expression of the molluscan brain trying to figure out the best way to eat this particular sea-weed. If so, such variability should be selectively enhanced by reward learning. Is it? Other questions:

• How is behavioural/neuronal variability generated in small and large brains?
• What % of behavioural/neuronal variability is really subject to learning/operant control in different networks?
• What features of neuronal activity are most likely to be subject to learning/operant control? In other words, where do we look? Spike rate of individual neurons? Network patterns? Duration of the different phases of motor programs?
• How is reward conditioning/operant control of spontaneous variability instantiated in small and large brains?
• How can we incorporate output-input functions in artificial neural networks and robotics? That is, what kind of tasks could such networks realistically perform today or in the future?
• What is the cultural effect (within in the neuroscience community and generally) of treating brains as output/input devices rather than input/output devices?

P.S. It was particularly stupid of me to emphasise the input-output side of things on the iPlant website, as the whole point of conditional rewarding brain stimulation is to modify output-input learning by rewarding beneficial but endogenously under-rewarded behavioural variations (rigorous exercise in morbidly obese patients etc.) with electrical pulses to the reward system.

iPlant fiction - Chapter 3

This is the third chapter of my novel-in-progress. This and previous chapters are available on the main website.

- "Every time, every time we meet she's late"
Lucy and Ike stood waiting outside D's assistant's office. The glass door was shut and the room inside in semi-darkness. The assistant was almost twenty minutes late.
- "Dopamine deficiency, swear to God", Lucy said.
- "Which one?", Ike said.
- "Midbrain insufficiency. Plain cell numbers, not enough dopamine."
- "Not a receptor problem? D1, D2? Unresponsive adrenal glands?"
- "Adrenal problems don't cause chronic lateness, she relies on her adrenal stress response to get her ass off the couch in the morning, but that doesn't kick in until she's critically late and then there's terrible traffic or some shit and we end up loosing our fucking morning staring at her door.."
- "Never heard you curse before", Ike said.
- "Period", Lucy said, holding her elbow and stepping restlessly on the spot.
- "D1 then? D2? Receptors not growing the way they should?"
- "Midbrain insufficiency"
- "How do you know? How would you know without scanning her? You got her scans??"
- "No. I just know."
- "Bullshit"
- "Fuck you"
They glared at each other for a brief moment.
"It's not D1", Lucy said, "because she's not inattentive and certainly not impulsive. And it's not D2 because she's a vicious learner, not just memoranda but procedure as well, that's why D hired her."
- "When was that?"
- "Same as me, for a while I thought we'd work together - her background is biotech and biomedical patents - but she's all administration now and real close to D."
- "Balanced D1 and D2 deficienciencies then? Hyperactive dopamine transporter?"
- "Knew you'd say that"
- "Well?"
- "You're pretty obvious Ike, as a person"
- "You're stalling"
- "Midbrain insufficiency. Not enough dopamine neurons."
- "How could you possibly know that without looking at her scans?!"
- "Calm down", Lucy said and lowered her voice as a small group of people emerged from the elevator at the end of the corridor and disappeared around a corner. "Look, first of all Meg and I agree on it and that's rare and I trust her judgement when it comes to guessing phenotypes and so should you. Second, Marlena is unstable, not in a way that really impacts her work but she's selectively anhedonic, severely - sometimes she truly doesn't see the point or doesn't care unless she's told and I bet you she's a lot less polished at home. But it's a partial problem and if you don't look for it you might not notice: and that's the point, receptor deficiencies have a smooth psychological profile, transporter deficiencies doubly so. Marlena's problem comes in patches. Third, look at her forehead! I'm not saying she's got a small midbrain, I'm saying her forebrain is oversized and sometimes she doesn't have the dopamine to keep all her units running, especially in the morning, which is why we're standing here wasting time."
Ike watched her speak.
- "Don't you ever tell anyone what I just said", Lucy said and suddenly looked nervous.
- "Course not"
- "I shouldn't have said all that"
- "I'm not telling, why would I tell?"
- "Shouldn't have said that"
- "Look, we're not gonna work well together if you keep distrusting me"
- "'Keep'?"
Ike paused, unsure.
- "Meg", he said finally, "You're trying to protect her from me"
Lucy burst into a high laugh.
- "Don't wanna sound cliché or theatrical but I'm more concerned about what she'll do to you, if you step on her feet. Do whatever you want, just don't fuck up so you can't work together."
- "How about some pointers then? What do you mean 'what she'll do' to me? She 'unstable' too?"
- "Oh no, I've gossiped more than enough"
They were silent for a while.
- "How about you tell me something?", Lucy said after a while, "How about you tell me where you got that scar?" She stroked the left side of her jaw, indicating a thick scar on his.
- "Stepped on someone's feet", Ike mumbled.
Marlena suddenly appeared from the elevator at the end of the hallway and hurried towards them.
- "I'm so sorry I'm late", she said, "Traffic's terrible and it's raining. Please come along."
Lucy and Ike looked with surprise at eachother as they followed Marlena down the corridor towards D's office, which she opened with a metal key.
- "We need Ike fully installed by the end of the day", Marlena said. She sat down behind D's large black desk, roused his computer with a quick mouse shake, typed out a long string of characters and hit enter unnecessarily hard. The computer logged in, showing the company logo against a dark background. She gestured for them to sit down in two easy chairs opposite the desk. "Water?" She fished up a bottle of sparkling mineral water from a drawer.
- "No thanks", they both said, attentive.
Marlena paused and looked at them.
- "You've been hired", she finally said to Ike, "I thought you knew."
Ike beamed.
- "D wants you installed and ready to work by the end of the day, you're going with the others to Brussels tomorrow."
- "That's excellent!", Ike exclaimed.
- "You need to bring your scans, we need you to discuss them with some people from the council"
There was a pause.
- "The brain scans", Marlena continued, looking steadily at him "You and Chris used his new ligands to make scans of your brain. You imaged your serotonin system a week ago in the PET scanner. You found substantial changes."
- "Chris told you?", Ike said, "He told D? He said I'd get him fired if I told anyone. So did you.", he turned to Lucy.
- "I don't know anything about this", Lucy said and held up her hands "don't particularly want to know"
- "You're going to Brussels to determine the council's true limits on experimental and commercial deep brain stimulation", Marlena said, "You want to work here because, one day, you want to undergo such surgery yourself - sooner rather than later I understand"
- "I want an iPlant", Ike said.
- "The iPlant is a theoretical construct as far as human application is concerned", Marlena said. "We need a battery of permissions and suspicions cleared before we can proceed with surgery. You're going to Brussels to test the European medical law authorities on that particular point. You'll pursue the argument that our implants and surgical procedure are worth the risks of surgery to customers who have never been hospitalized but who might nevertheless consider themselves neurologically handicapped. Your scans will provide a vivid example of such a case."
- "Do we really want to use one unauthorized procedure to get permission for another?", Lucy asked.
- "You're not going there to get permisison, just to test the waters..", Marlena began.
- "I know", Lucy said, "And to be frank we'll probably proceed with the iPlant either way. I'm asking whether these scans might do more harm than good."
- "D tells me they are quite convincing", Marlena said and looked at Ike.
The three fell silent for a moment.
- "Jeez Ike", Lucy finally said, "How much ecstasy did you have?"
- "It makes sense", Ike said, "I'm in"
- "Brilliant", Marlena said and began filling out a form she'd pulled up on the screen.
- "How much did you have?", Lucy asked again.
- "Enough", Ike said.
- "If you'll come with me over here..", Marlena said and led Ike over to an eye and finger-scanner beside a small safe in the far corner of the room, next to a large liquor cabinet. "Just place your fingertips here please.. and look at the white dot there.. and again.. excellent."

And here I was thinking us humans couldn't build running robots

Notes on electrical rhythms in the brain

I'm reading George Buszáki's Rhythms of the Brain at the moment. Here are some notes on what I've read so far. Please correct me if I've got something wrong.

Electrical fluctuations in the cortex are organized into rhytmic oscillations at different spatial and temporal scales. The resting cortex is characterized by oscillations primarily in the alpha band (8-12 Hz, the brain's 'default network'). The active (i.e. behaving, percieving) cortex is characterized by oscillations primarily in the gamma band (25-100 Hz). Buszáki and others argue that cortical neurons that synchronize their membrane oscillations in the gamma band 'bind' their respective functions (e.g. visual feature detection) together into cognitive processes (e.g. object perception). Such formations of neurons are called neuronal groups or assemblies. Particularly striking are neuronal groups in the gamma range emerging in the prefrontal cortex for the duration of time that human patients are asked to hold items in working memory.

(alpha)

(gamma)

Cortical neurons sponaneously synchronize their membrane oscillations in the gamma range and form transient neuronal groups even in the absence of stimuli. This is, at least in part, due to the time constants of GABA curents, synaptic delays and synaptic potentiation. Buszáki writes:

"If neurons are already engaged in internal synchronization, the external stimulus will compete with the central oscillator, and the coutcome depends on the relative timing and strenght of the external input and the propensity of the internal oscillator. The stimulus may be ignored, or it may enhance or quench the internal oscillation." p.255

In other words, the effect of a stimulus on cortical activity depends strongly on the prior state of the brain. This explains the significant variability in brain activity (e.g. on EEG/MEG/fMRI) seen within and between subjects in response to invariant stimuli. Buszáki laments the fact that this variability is usually averaged out and treated as 'noise'. Björn Brembs often makes a similar argument.

Stimuli interact with ongoing cortical activity in various ways. Whereas a weak stimulus may reset the phase of ongoing oscillations, a strong or salient stimulus may completely change the type and distribution of oscillations in the cortex. Several studies have found that strong ongoing oscillations in the gamma, theta or alpha ranges prior to stimulus presentation promote efficient memory encoding. A stimulus that resets a strong rhythm presumably has a larger impact on brain activity than one that resets a weak rhythm. The presence or absence of strong rhythms in the brain is directly related to states of attention and catecholamine concentrations.