Review, Hollan & Gorodnitsky

Adrienne Moore, by email

2-20-08

adriennermoore@yahoo.com

Affordances

• “An affordance refers to a physical property of something that influences how it can be used. For example, the affordances of paper include its properties for being viewed, it's light weight, and so on. The nature of a handle on a door determines how one opens the door -- by pulling, or pushing, or twisting, and so on.”

• One of the great affordances of computers/digital media is Plasticity– Computation is very flexible– It can mimic other media or do entirely new things (so it’s a

metamedium)

New technologies in HCI (know a little about what they are and how they work):

• Morphable Model (3-D face synthesizer)– Morphing Ethnicity

• Seam carving for context aware image resizing • Multitouch – perceptive pixels • Surfaces:

– Visionmaker desk, Augmented Surfaces, Microsoft Surface

– The Everywhere Displays project• Bridging paper and digital:

– Digital Pens (Anoto)– Papiercraft

Brain oscillations by frequency (Hz)

• Slow wave (< 1 Hz) & Delta (1-4 Hz)

• Theta – (4-8 Hz):2 sorts, hippocampal & cortical

• Alpha – (8-12 Hz): 3 sorts, occipital alpha (visual), central mu (motor), temporal tau (auditoty)

• Beta – (12-30 Hz)

• Gamma – (30-100 Hz)

Brain Oscillation + Related Functions/Mental States

• Slow wave & Delta: deep sleep• Hippocampal Theta: many aspects of memory; balance,

spatial navigation• Cortical Theta: sleep, drowsiness, relative “absence”,

sadness (low arousal states); forming new episodic memory

• Alpha: relaxed inattentiveness, relative “presence”, eyes shut, inhibiting information flow perhaps– A lot of alpha/mu/tau means you’re NOT doing something (not using

your visual, motor, or auditory brain)

• Beta: alert & focused, anxious (higher arousal states); long distance synchronization of brain activity

• Gamma: synchronization of brain activity in local, neighboring brain areas

A little more on Alpha

• Alpha: relaxed inattentiveness, relative “presence”, eyes shut, inhibiting information flow perhaps– Relative presence because you could respond to your

environment (you’re not too sleepy yet)– A lot of alpha/mu/tau power means you’re NOT doing something

(not using your visual, motor, or auditory brain)– A lot of occipital alpha means your visual system is idling or

going off-line; A lot of temporal alpha/tau means your auditory system is going off-line

– A lot of central alpha/ mu means your somatotopically mapped motor system (remember, homunculus) is going off-line

• a lot of hand related mu can mean you’re using your mouth and inhibiting your hand; a lot of mouth related mu can mean you’re using your hand and inhibiting your mouth

Synchrony

• Synchrony = neurons firing in phase/at the same time

• Synchronous electrical brain activity sums, and therefore its effect is large enough to record with electrodes at the scalp

• Synchrony may allow the brain to bind networks together, & to coordinate the timing of distinct brain regions that have to interact

Brain Oscillations Can Be Useful

• Uses include:• Biofeedback: for stress reduction & relaxation • Deep brain stimulation: a surgical treatment that

implants a “brain pacemaker” , which electrically stimulates specific brain areas. Treats movement and affective disorders such as chronic pain and Parkinson’s Disease

• BCI: uses EEG to allow patients with locked-in syndrome to communicate with the world by thinking at a computer

Types of BCIs

• P300 BCI– P300 = a positive event-related potential

(ERP) seen 300 milliseconds after an “event”– The “event” might be seeing a target

• + is the target. -,-,-,-,-,-,-,+ You just generated a P300! This can be used to control a computer by mind power alone, even if your body is completely paralyzed

Types of BCIs

• Mu BCI– Remember the EEG mu rhythm is related to mirror

neuron type activity – Mirror neurons fire when you merely observe a

movement ; mu rhythm is desynchronized when you merely imagine a movement

• (imagining = mental imagery = simulating something in your mind and observing your simulation. roughly speaking.)

– So, by simulating movement in your mind, even if you can’t actually move, you could control a computer

Types of BCIs

• Steady state visual evoked potential (SSVEP) BCI– What’s an SSVEP? When the retina is excited by a

visual stimulus (e.g. a blinking light) of a particular frequency, the brain generates oscillatory electrical activity at the same frequency

– So if you can control your eyes but not the rest of your body, you could operate a computer by looking at stimuli of different frequencies

Good-bye

I’m very sorry I missed section today (again!). But I think you are in good shape

for the midterm anyhow. Feel free to email me or post remaining questions to

the website discussion forum!!