The neural correlates of maternal and romantic love

Romantic and maternal love are highly rewarding experiences. Both are linked to the perpetuation of the species and therefore have a closely linked biological function of crucial evolutionary importance. Yet almost nothing is known about their neural correlates in the human. We therefore used fMRI to measure brain activity in mothers while they viewed pictures of their own and of acquainted children, and of their best friend and of acquainted adults as additional controls. The activity specific to maternal attachment was compared to that associated to romantic love described in our earlier study and to the distribution of attachment-mediating neurohormones established by other studies. Both types of attachment activated regions specific to each, as well as overlapping regions in the brain's reward system that coincide with areas rich in oxytocin and vasopressin receptors. Both deactivated a common set of regions associated with negative emotions, social judgment and 'mentalizing', that is, the assessment of other people's intentions and emotions. We conclude that human attachment employs a push-pull mechanism that overcomes social distance by deactivating networks used for critical social assessment and negative emotions, while it bonds individuals through the involvement of the reward circuitry, explaining the power of love to motivate and exhilarate.

The chronoarchitecture of the human brain—natural viewing conditions reveal a time-based anatomy of the brain

A dominant tendency in cerebral studies has been the attempt to locate architecturally distinct parts of the cortex and assign special functions to each, through histological, clinical or hypothesis-based imaging experiments. Here we show that the cerebral cortex can also be subdivided into different components temporally, without any a priori hypotheses, based on the principle of functional independence. This states that distinct functional subdivisions have activity time courses (ATCs) that are, if not independent, at least characteristic to each when the brain is exposed to natural conditions. To approach a time-based anatomy experimentally, we recorded whole-brain activity using functional magnetic resonance imaging (fMRI) and analyzed the data with independent component analysis (ICA). Our results show that a multitude of cortical areas can be identified based purely on their characteristic ATCs during natural conditions. We demonstrate that a more "rich" stimulation (free viewing of a movie) leads to more areas being activated in a specific way than conventional stimuli, allowing for a more detailed dissection of the cortex into its subdivisions. We show that stimulus-driven functionally specialized areas can be identified by intersubject correlation even if their function is unknown. Chronoarchitectonic mapping thus opens the prospect of identifying previously unknown cortical subdivisions based on natural viewing conditions by exploiting the characteristic temporal "fingerprint" that is unique to each.

Functional brain mapping during free viewing of natural scenes

Previous imaging studies have used mostly perceptually abstracted, idealized, or static stimuli to show segregation of function in the cerebral cortex. We wanted to learn whether functional segregation is maintained during more natural, complex, and dynamic conditions when many features have to be processed simultaneously, and identify regions whose activity correlates with the perception of specific features. To achieve this, we used functional magnetic resonance imaging (fMRI) to measure brain activity when human observers viewed freely dynamic natural scenes (a James Bond movie). The intensity with which they perceived different features (color, faces, language, and human bodies) was assessed psychometrically in separate sessions. In all subjects different features were perceived with a high degree of independence over time. We found that the perception of each feature correlated with activity in separate, specialized areas whose activity also varied independently. We conclude that even in natural conditions, when many features have to be processed simultaneously, functional specialization is preserved. Our method thus opens a new way of brain mapping, which allows the localization of a multitude of brain areas based on a single experiment using uncontrolled, natural stimuli. Furthermore, our results show that the intensity of activity in a specialized area is linearly correlated with the intensity of its perceptual experience. This leads us to suggest that each specialized area is directly responsible for the creation of a feature-specific conscious percept (a microconsciousness). Hum. Brain Mapp. 21:75-83, 2004.

Absolute-frequency measurements with a stabilized near-infrared optical frequency comb from a Cr:forsterite laser

A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8 microm. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this comb we measured two frequency references in the telecommunications band: one half of the frequency of the d/f crossover transition in 87Rb at 780 nm, and the methane v2 + 2v3 R(8) line at 1315 nm.

420-MHz Cr:forsterite femtosecond ring laser and continuum generation in the 1-2-micrometre range

We demonstrate a chromium-doped forsterite femtosecond ring laser that generates 30-fs pulses at a 420-MHz repetition rate with nearly 500 mW of average power. The compact solid-state design and broad spectral output make this laser attractive for telecommunications applications in the 1.3-1.5-micrometre region. Additional spectral broadening of the laser output in highly nonlinear optical fiber leads to octave-spanning spectra ranging from 1.06 to 2.17 micrometre. The octave is reached at a level of 18 dB below the peak. The underlying optical frequency comb can be linked to existing optical frequency standards.

Mode-locked laser pulse trains with subfemtosecond timing jitter synchronized to an optical reference oscillator

We independently phase lock the repetition rates of two femtosecond lasers at their approximately 456, 000th harmonic to a common optical oscillator. The timing jitter of each individual laser relative to the optical reference is only 0.45 fs in a 100-Hz bandwidth. Our method takes advantage of the tremendous leverage that is possible when stability is transferred from the optical to the microwave domain. The low timing jitter is commensurate with the independently measured fractional frequency instability in the repetition rates of < or = 2.3 x 10(-15) in 1-s averaging time, limited by the measurement system. The microwave signals at 1 GHz that are extracted by photodetection of the pulse trains have a 10-times-greater instability, confirming the presence of excess noise in the photodetection.

The processing of kinetic contours in the brain

This work investigates whether the brain assigns special cortical areas for the processing of kinetic contours. In human imaging experiments, we compared the brain activity produced in the so-called 'kinetic occipital' area ('KO') when humans perceive shapes generated from kinetic boundaries or from equiluminant colors. 'KO' was activated whenever subjects perceived shapes, no matter how they were derived; it is therefore not specialized for the processing of kinetic contours. The application of independent component analysis (ICA) to imaging data obtained when subjects viewed 22 min of an action movie showed that the time course of activity in 'KO' correlates better with activity in area V3 than with activity in two adjacent areas, V5 and LO. We thus consider 'KO' to be part of the V3 family of areas, and use the terminology of Smith et al. (J Neurosci 18:3816-3830, 1998), to refer to it as area V3B. Recordings from orientation-selective cells in the macaque V3 complex show that the great majority have the same orientational specificity when tested with oriented lines generated from kinetic stimuli or from luminance differences. We conclude that there is no present evidence for a visual area specialized for the processing of kinetic contours in the primate visual brain.

Generation of a broadband continuum by a Ti:sapphire femtosecond oscillator with a 1-GHz repetition rate

A five-element Ti:sapphire femtosecond ring oscillator emitting a broadband continuum that ranges from 560 to 1150 nm at -50 dB below the maximum with a repetition rate of 1 GHz is demonstrated. The key element is a slightly convex cavity mirror that increases the self-amplitude modulation of a short pulse inside the resonator. Flat negative intracavity group-delay dispersion is required only for the core spectral part of the pulse. We believe that the device presented will make optical frequency metrology and future optical atomic clocks simpler and more stable. Within the reported ultrabroad spectrum a distinct strong emission band near 655 nm occurs that can be extracted to a powerful femtosecond pulse source far out of the amplification of Ti:sapphire.

Phase-coherent link from optical to microwave frequencies by means of the broadband continuum from a 1-GHz Ti:sapphire femtosecondoscillator

An optical clockwork is created with a compact 1-GHz repetition-rate laser and three nonlinear crystals. The broadband continuum output of the laser covers sufficient bandwidth to provide direct access to its carrier-envelope offset frequency without the use of a microstructure fiber. We phase lock the femtosecond comb to a Ca optical standard and monitor the stability of the repetition rate, f(r) , at 1 GHz. We demonstrate that the short-term stability of the microwave output of the optical clock is at least as good as that of a high-performance hydrogen maser.

The neural basis of romantic love

The neural correlates of many emotional states have been studied, most recently through the technique of fMRI. However, nothing is known about the neural substrates involved in evoking one of the most overwhelming of all affective states, that of romantic love, about which we report here. The activity in the brains of 17 subjects who were deeply in love was scanned using fMRI, while they viewed pictures of their partners, and compared with the activity produced by viewing pictures of three friends of similar age, sex and duration of friendship as their partners. The activity was restricted to foci in the medial insula and the anterior cingulate cortex and, subcortically, in the caudate nucleus and the putamen, all bilaterally. Deactivations were observed in the posterior cingulate gyrus and in the amygdala and were right-lateralized in the prefrontal, parietal and middle temporal cortices. The combination of these sites differs from those in previous studies of emotion, suggesting that a unique network of areas is responsible for evoking this affective state. This leads us to postulate that the principle of functional specialization in the cortex applies to affective states as well.

Coupled bloch-phonon oscillations in semiconductor superlattices

We investigate coherent Bloch oscillations in GaAs/AlxGa1-xAs superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be tuned into resonance with the optical phonon. Close to resonance a direct coupling of Bloch oscillations to LO phonons is observed which gives rise to the coherent excitation of LO phonons. The density necessary for driving coherent LO phonons via Bloch oscillations is about 2 orders of magnitude smaller than the density necessary to drive coherent LO phonons in bulk GaAs. The experimental observations are confirmed by the theoretical description of this phenomenon [A.W. Ghosh et al., Phys. Rev. Lett. 85, 1084 (2000)].

Impulsive excitation of phonon-pair combination states by second-order raman scattering

The excitation of (100)-oriented KTaO3 with 25-fs laser pulses impulsively drives phonon-pair combination states via second-order Raman scattering. Oscillations in the phonon-amplitude covariance at the sum and difference frequency of the two involved phonons are observed in a spectrally and temporally resolved pump-probe experiment. Transmission changes of the sample are dominated by contributions of wave vector conserving phonon-pair combinations from the entire Brillouin zone that have maxima in their combined density of states. For low temperatures the temperature dependence of the covariance oscillations of different phonon combinations is reproduced by a quantum-mechanical model.

The architecture of the colour centre in the human visual brain: new results and a review

We have used the technique of functional magnetic resonance imaging (fMRI) and a variety of colour paradigms to activate the human brain regions selective for colour. We show here that the region defined previously [Lueck et al. (1989) Nature, 340, 386-389; Zeki et al. (1991) J. Neurosci., 11, 641-649; McKeefry & Zeki (1997) Brain, 120, 2229-2242] as the human colour centre consists of two subdivisions, a posterior one, which we call V4 and an anterior one, which we refer to as V4alpha, the two together being part of the V4-complex. The posterior area is retinotopically organized while the anterior is not. We discuss our new findings in the context of previous studies of the cortical colour processing system in humans and monkeys. Our new insight into the organization of the colour centre in the human brain may also account for the variability in both severity and degree of recovery from lesions producing cerebral colour blindness (achromatopsia).

The clinical and functional measurement of cortical (in)activity in the visual brain, with special reference to the two subdivisions (V4 and V4 alpha) of the human colour centre

We argue below that, at least in studying the visual brain, the old and simple methods of detailed clinical assessment and perimetric measurement still yield important insights into the organization of the visual brain as a whole, as well as the organization of the individual areas within it. To demonstrate our point, we rely especially on the motion and colour systems, emphasizing in particular how clinical observations predicted an important feature of the organization of the colour centre in the human brain. With the use of data from functional magnetic resonance imaging analysed by statistical parametric mapping and independent component analysis, we show that the colour centre is composed of two subdivisions, V4 and V4 alpha the two together constituting the V4 complex of the human brain. These two subdivisions are intimately linked anatomically and act cooperatively. The new evidence about the architecture of the colour centre might help to explain why the syndrome, cerebral achromatopsia, produced by lesions in it is so variable.

Femtosecond Ti:sapphire ring laser with a 2-GHz repetition rate and its application in time-resolved spectroscopy

A Kerr-lens mode-locked femtosecond Ti:sapphire laser operating at a repetition rate of 2 GHz is demonstrated. A mirror-dispersion-controlled unidirectional ring cavity delivers nearly bandwidth-limited pulses of 23-fs length. Mode locking is self-starting without a hard aperture in the cavity. The advantages of this high-repetition-rate oscillator in optical time-resolved spectroscopy are demonstrated.

Toward a theory of visual consciousness

The visual brain consists of several parallel, functionally specialized processing systems, each having several stages (nodes) which terminate their tasks at different times; consequently, simultaneously presented attributes are perceived at the same time if processed at the same node and at different times if processed by different nodes. Clinical evidence shows that these processing systems can act fairly autonomously. Damage restricted to one system compromises specifically the perception of the attribute that that system is specialized for; damage to a given node of a processing system that leaves earlier nodes intact results in a degraded perceptual capacity for the relevant attribute, which is directly related to the physiological capacities of the cells left intact by the damage. By contrast, a system that is spared when all others are damaged can function more or less normally. Moreover, internally created visual percepts-illusions, afterimages, imagery, and hallucinations-activate specifically the nodes specialized for the attribute perceived. Finally, anatomical evidence shows that there is no final integrator station in the brain, one which receives input from all visual areas; instead, each node has multiple outputs and no node is recipient only. Taken together, the above evidence leads us to propose that each node of a processing-perceptual system creates its own microconsciousness. We propose that, if any binding occurs to give us our integrated image of the visual world, it must be a binding between microconsciousnesses generated at different nodes. Since any two microconsciousnesses generated at any two nodes can be bound together, perceptual integration is not hierarchical, but parallel and postconscious. By contrast, the neural machinery conferring properties on those cells whose activity has a conscious correlate is hierarchical, and we refer to it as generative binding, to distinguish it from the binding that might occur between the microconsciousnesses.

Umbilical one-puncture laparoscopic-assisted appendectomy in children

To perform a laparoscopic appendectomy, three trocars are usually needed. In order to reduce abdominal wall trauma, we have adopted an umbilical one-puncture laparoscopic-assisted appendectomy (UOPLAA). We did a retrospective study of UOPLAA performed during last 2 years on 200 children aged from 5 to 18 years (median, 9 years). The patients were selected after clinical examination. No child with advanced generalized peritonitis or an abscess with a palpable mass was a candidate for this technique. UOPLAA was successful in 184 patients (92%). In 16 cases (8%), an additional trocar was required to manage perforated or retrocecal appendicitis. The mean operative time was 15 min, and the mean hospital stay was 2 days. There were no intraoperative complications. There were 10 (5%) postoperative complications (three parietal and seven intraabdominal). Four patients (2%) needed reoperation under general anesthesia. The UOPLAA is our preference in cases of acute nonperforated appendicitis because it is simple and fast, with good cosmetic results; but in 8% of our cases, an intraoperative difficulty (retrocecal location, abnormal adhesive band, peritonitis, etc.) arose that required the introduction of additional devices to ensure the safety of the laparoscopic procedure.

The theory of multistage integration in the visual brain

The theory of multistage integration is based on evidence that the visual brain consists of several parallel multistage processing systems, each specialized for a given attribute such as colour or motion. Each stage of a given system processes information at a distinct level of complexity. Our theory supposes that activity at any stage of a given multistage processing system is perceptually explicit--that is to say, it requires no further processing to generate a conscious experience. This activity can be integrated, or bound, with the perceptually explicit activity at any given stage of another or the same multistage processing system. Such binding is therefore not a process that generates a conscious experience, but rather one that brings different conscious experiences together. Many perceptual advantages result from such a flexible and dynamic integrative system. Conversely, there would be disadvantages to limiting perception and binding to hypothetical 'terminal' stages of such processing systems or to hypothetical 'integrator' areas. Although we formulate our hypothesis in terms of the visual brain, we believe it might form a general principle of brain functioning.

The autonomy of the visual systems and the modularity of conscious vision

Anatomical and physiological evidence shows that the primate visual brain consists of many distributed processing systems, acting in parallel. Psychophysical studies show that the activity in each of the parallel systems reaches its perceptual end-point at a different time, thus leading to a perceptual asynchrony in vision. This, together with clinical and human imaging evidence, suggests strongly that the processing systems are also perceptual systems and that the different processing-perceptual systems can act more or less autonomously. Moreover, activity in each can have a conscious correlate without necessarily involving activity in other visual systems. This leads us to conclude not only that visual consciousness is itself modular, reflecting the basic modular organization of the visual brain, but that the binding of cellular activity in the processing-perceptual systems is more properly thought of as a binding of the consciousnesses generated by each of them. It is this binding that gives us our integrated image of the visual world.

The asynchrony of consciousness

We present below a simple hypothesis on what we believe is a characteristic of visual consciousness. It is derived from facts about the visual brain revealed in the past quarter of a century, but it relies most especially on psychophysical evidence which shows that different attributes of the visual scene are consciously perceived at different times. This temporal asynchrony in visual perception reveals, we believe, a plurality of visual consciousnesses that are asynchronous with respect to each other, reflecting the modular organization of the visual brain. We further hypothesize that when two attributes (e.g. colour and motion) are presented simultaneously, the activity of cells in a given processing system is sufficient to create a conscious experience of the corresponding attribute (e.g. colour), without the necessity for interaction with the activities of cells in other processing systems (e.g. motion). Thus, any binding of the activity of cells in different systems should be more properly thought of as a binding of the conscious experiences generated in each system.

The spatiotemporal transfer function of crayfish lamina monopolar neurons

1. The graded, synaptic potentials of first-order visual interneurons (lamina monopolar cells) were examined with intracellular recordings. The spatiotemporal properties were characterized with drifting sine wave gratings and annuli. 2. Annulus-elicited inhibition is maximal for annulus-test pulse intervals of approximately 140 ms and declines exponentially. The inhibition declines with increasing annular internal radii (ri). 3. Grating responses were examined with respect to spatial and temporal frequency. The gratings elicit sinusoidal signals that are approximately linear with contrast. 4. Variations in spatial frequency produce response functions with a low-pass or modest band-pass characteristic, which are described by a difference of Gaussians sensitivity profile. The central Gaussian approximates the sensitivity profile of photoreceptors. The inhibitory Gaussian is similar to the inhibitory field estimated with annulus pulses. The peak of the inhibitory Gaussian is approximately 18% of the peak excitatory Gaussian. 5. Variations in temporal frequency generally produce transfer functions with a band-pass characteristic and a peak at 1.0 Hz. These data were described by a difference of exponentials function convolved with a low-pass filter that approximates the photoreceptor response. The inhibitory time course estimated from these data was similar to that of the annulus measurements. 6. The spatiotemporal properties of lateral inhibition are consistent with inhibitory action by the lamina amacrine neurons. The proposed model is spatiotemporally inseparable and nonrecurrent. 7. Eleven of 20 monopolar cells tested exhibited a strong orientation preference with a bias to the vertical. Photoreceptors exhibit little or no orientation preference.

Non-invasive determination of systolic blood pressure by heart sound pattern analysis

A new concept of non-invasive blood pressure measurement by heart sound pattern analysis is described. The known diagnostic criterion of the 'accentuated' second heart sound of a hypertensive patient is here converted into a computer-aided pattern-recognition process for the second heart sound, applicable over the entire scale of blood pressure. After a 'learning phase', during which the second heart sound is recorded, analysed and correlated with a set of systolic blood pressure values of the individual patient, the computer is able to determine systolic blood pressure of the same patient from the acoustic spectrum of the second heart sound with sufficient precision. The method is in principle suited for automatically repeated blood pressure measurements, but further development is still needed for conversion into a widely practicable procedure.

[Control of the placement of a central venous catheter using Doppler ultrasound]

Precise placement of central venous catheters is necessary to prevent complications and assure proper functioning. Chest X-ray is the current standard method of locating the catheter tip. This is usually not feasible in the operating room setting, particularly after the induction of anesthesia. Intravascular ECG registration using the catheter as a lead and identification of intra-atrial P-waves has been suggested as an alternative. In the present study we evaluated the use of Doppler sonography as a noninvasive method of locating the catheter tip and detecting faulty placement. Two hundred patients scheduled for insertion of a central venous catheter took part in this study. The catheters were inserted via standard routes (internal or external jugular vein, basilar or cephalic vein). A Doppler sonographic device with a 2 mHz probe was used (Parke Electronics 915L). The probe was applied to the right sternal border and affixed at the position where the characteristic venous flow sound was most distinct. The signals were displayed visually, subjected to spectral analysis, and also recorded for later evaluation. A rapid injection of 2-5 ml isotonic saline causes turbulences which can readily be heard and recognized without special training. The position of every catheter was later confirmed by radiography, and in 159 patients the intraatrial ECG method was subjected to direct comparison with the sonographic method. The turbulences due to the injected fluid were found to cause an increased amplitude at frequencies above 350 Hz. If the catheter tip was positioned correctly there was no discernable time lag between the start of the injection and perception of turbulences.(ABSTRACT TRUNCATED AT 250 WORDS)