Functional Brain Imaging

Functional Brain Functional Brain ImagingImagingIn the last few years there have been In the last few years there have been tremendous advances in brain tremendous advances in brain imaging. This course will introduce imaging. This course will introduce you to the various techniques used you to the various techniques used to measure functional activity of the to measure functional activity of the living brain. The focus of the course living brain. The focus of the course will be on the way that these new will be on the way that these new techniques can be exploited to techniques can be exploited to study human mental processesstudy human mental processes..

Functional Brain Functional Brain ImagingImagingImaging methods covered:Imaging methods covered: Computed tomographyComputed tomography PET / SPECTPET / SPECT MRIMRI fMRI – BOLDfMRI – BOLD EEGEEG ERPERP MEGMEG

We will learn the physical and technical bases of We will learn the physical and technical bases of each method and will see examples of recent each method and will see examples of recent research reports research reports

HistoryHistory Franz Joseph Gall: (early Franz Joseph Gall: (early

1800s)1800s)mental processes emerge mental processes emerge from the brain,from the brain,are performed by functionally are performed by functionally separate components separate components (the components can be (the components can be measured by palpable measured by palpable protrusions beneath the scalp protrusions beneath the scalp = phrenology)= phrenology)

Throughout the 19-20Throughout the 19-20thth centuries, researchers have centuries, researchers have been trying to define the been trying to define the various functional components various functional components of the brain (neophrenology?)of the brain (neophrenology?)

History (2)History (2)

Neuropsychology: Learning about Neuropsychology: Learning about functional components by studying functional components by studying lessionslessions

Broca, Wernicke (1860-1870)Broca, Wernicke (1860-1870) Problem with this : A cogwheel Problem with this : A cogwheel

with missing teeth makes noise. Is with missing teeth makes noise. Is the function of a missing tooth of the function of a missing tooth of the cogwheel to silence the noise?the cogwheel to silence the noise?

History (3)History (3) Broca (1870) used Broca (1870) used

temperature probes placed temperature probes placed on the skull to show that on the skull to show that specific mental activity specific mental activity causes increased blood causes increased blood flow and temperature flow and temperature change in key brain areas, change in key brain areas, but not in other parts of the but not in other parts of the body.body.

Hans Berger also studied it Hans Berger also studied it but turned to develop the but turned to develop the encephalographencephalograph

Angelo Mosso (1880) Angelo Mosso (1880) observed changes in blood observed changes in blood flow in 3 patients with skull flow in 3 patients with skull lessionslessions

History (4)History (4) Whenever the Whenever the

patients were patients were spoken to, began spoken to, began thinking actively, thinking actively, or was emotionally or was emotionally aroused there was aroused there was an immediate an immediate increase in intra-increase in intra-cranial blood cranial blood pressurepressure

History (5)History (5) Interest in this kind of research Interest in this kind of research

stopped until 1928, in part due to the stopped until 1928, in part due to the lack of adequate technology, but also lack of adequate technology, but also due to the influence of Hill, who due to the influence of Hill, who claimed there was no relation between claimed there was no relation between brain function and brain circulationbrain function and brain circulation

Fulton (1928) reported about a patient Fulton (1928) reported about a patient with an artery malformation in the with an artery malformation in the occipital cortex. The blood flow in the occipital cortex. The blood flow in the artery could be listened to with a artery could be listened to with a stethoscope.stethoscope.

History (6)History (6) The changes in cortical blood flow related The changes in cortical blood flow related

to the complexity of the visual task and to the complexity of the visual task and the attention of the subject to that taskthe attention of the subject to that task

History (7)History (7) The next big step was in the 1950s, The next big step was in the 1950s,

when Seymour Kety and colleagues when Seymour Kety and colleagues developed the first quantitative developed the first quantitative methods for measuring whole brain methods for measuring whole brain blood flow and metabolism blood flow and metabolism in vivoin vivo in in humans. They provided the first glimpse humans. They provided the first glimpse of quantitative changes in blood flow of quantitative changes in blood flow related directly to brain function.related directly to brain function.

The only thing needed afterwards was The only thing needed afterwards was new computing power and algorithms new computing power and algorithms which came with the invention of the which came with the invention of the CT.CT.

History (8)History (8)

““Of course we recognize that this is a very Of course we recognize that this is a very secondhand way of determining secondhand way of determining physiological activity; it is rather like trying physiological activity; it is rather like trying to measure what a factory does by to measure what a factory does by measuring the intake of water and the measuring the intake of water and the output of sewage. This is only a problem of output of sewage. This is only a problem of plumbing and only secondary inferences plumbing and only secondary inferences can be made about function. We would not can be made about function. We would not suggest that this is a substitute for suggest that this is a substitute for electrical recording in terms of easy electrical recording in terms of easy evaluation of what is going on.’’evaluation of what is going on.’’

William Landau, American Neurological AssociationWilliam Landau, American Neurological Association

Modern Imaging Modern Imaging TechniquesTechniques

CT – based on X-raysCT – based on X-raysPET PET MRI, fMRIMRI, fMRIEEGEEGMEGMEG

X-rays: small wavelength = high energy

Tend to act more like particles than like waves

Are able to pass thru tissue. The denser tissues (bones) block more than less dense tissue (lungs). Dense=higher atomic weight

Special photographic film is used. X-rays are converted into light, the more energy the darker the area.

What we see in the picture are really the “shadows” that the dense tissue cast.

X-rays (Roentgen, 1895)

CT – Computed CT – Computed TomographyTomography

Tomos = section, sliceTomos = section, slice Based on x-raysBased on x-rays Instead of taking one Instead of taking one

picture, the x-rays are picture, the x-rays are rotated and a digital rotated and a digital picture of a thin slice is picture of a thin slice is computed.computed.

Multiple slices yield a 3D Multiple slices yield a 3D image of the internal image of the internal organsorgans

Also computed axial Also computed axial tomography (CAT)tomography (CAT)

CT animationCT animation

CT (1975). 128 x 128 matrix

State of the art CT. 512 x 512

Subtle differences in tissue density can be seen

Basic DensitiesBasic Densities

AirAir Fat & LipidFat & Lipid Soft tissue (muscle)Soft tissue (muscle) Calcium (bone)Calcium (bone) Contrast agent (e.g. iodine)Contrast agent (e.g. iodine) MetalMetal

Circle of Willis

Radiological convention

BOTTOMRIGHT SIDEFRONT

LEFT is RIGHT; RIGHT is LEFT

Nuclear medicine (neurological) convention

TOPRIGHT SIDEBACK

LEFT is LEFT; RIGHT is RIGHT

Axial

Transaxial

TransverseY

Z

X